How-To Tutorials

13 Feb 2014

4 min read

Adding Graphics to the Map

13 Feb 2014

(For more resources related to this topic, see here.) Graphics are points, lines, or polygons that are drawn on top of your map in a layer that is independent of any other data layer associated with a map service. Most people associate a graphic object with the symbol that is displayed on a map to represent the graphic. However, each graphic in ArcGIS Server can be composed of up to four objects, including the geometry of the graphic, the symbology associated with the graphic, attributes that describe the graphic, and an info template that defines the format of the info window that appears when a graphic is clicked on. Although a graphic can be composed of up to four objects, it is not always necessary for this to happen. The objects you choose to associate with your graphic will be dependent on the needs of the application that you are building. For example, in an application that displays GPS coordinates on a map, you may not need to associate attributes or display info window for the graphic. However, in most cases, you will be defining the geometry and symbology for a graphic. Graphics are temporary objects stored in a separate layer on the map. They are displayed while an application is in use and are removed when the session is complete. The separate layer, called the graphics layer, stores all the graphics associated with your map. Just as with the other types of layers, GraphicsLayer also inherits from the Layer class. Therefore, all the properties, methods, and events found in the Layer class will also be present in GraphicsLayer. Graphics are displayed on top of any other layers that are present in your application. An example of point and polygon graphics is provided in the following screenshot. These graphics can be created by users or drawn by the application in response to the tasks that have been submitted. For example, a business analysis application might provide a tool that allows the user to draw a freehand polygon to represent a potential trade area. The polygon graphic would be displayed on top of the map, and could then be used as an input to a geoprocessing task that pulls demographic information pertaining to the potential trade area. Many ArcGIS Server tasks return their results as graphics. The QueryTask object can perform both attribute and spatial queries. The results of a query are then returned to the application in the form of a FeatureSet object, which is simply an array of features. You can then access each of these features as graphics and plot them on the map using a looping structure. Perhaps you'd like to find and display all land parcels that intersect the 100 year flood plain. A QueryTask object could perform the spatial query and then return the results to your application, where they would then be displayed as polygon graphics on the map. In this article, we will cover the following topics: The four parts of a graphic Creating geometry for graphics Symbolizing graphics Assigning attributes to graphics Displaying graphic attributes in an info window Creating graphics Adding graphics to the graphics layer The four parts of a graphic A graphic is composed of four items: Geometry, Symbol, Attributes, and InfoTemplate, as shown in the following diagram: A graphic has a geometric representation that describes where it is located. The geometry, along with a symbol, defines how the graphic is displayed. A graphic can also have attributes that provide descriptive information about the graphic. Attributes are defined as a set of name-value pairs. For example, a graphic depicting a wildfire location could have attributes that describe the name of the fire along with the number of acres burned. The info template defines what attributes should be displayed in the info window that appears when the graphic appears, along with how they should be displayed. After their creation, the graphic objects must be stored inside a GraphicsLayer object, before they can be displayed on the map. This GraphicsLayer object functions as a container for all the graphics that will be displayed. All the elements of a graphic are optional. However, the geometry and symbology of a graphic are almost always assigned. Without these two items, there would be nothing to display on the map, and there isn't much point in having a graphic unless you're going to display it. The following figure shows the typical process of creating a graphic and adding it to the graphics layer. In this case, we are applying the geometry of the graphic as well as a symbol to depict the graphic. However, we haven't specifically assigned attributes or an info template to this graphic.

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4951

article-image-vmware-vcenter-operations-manager-essentials-introduction-vcenter-operations-manager

Packt

12 Feb 2014

14 min read

VMware vCenter Operations Manager Essentials - Introduction to vCenter Operations Manager

Packt

12 Feb 2014

14 min read

0
0
2917

How-To Tutorials

article-image-introduction-vsphere-distributed-switches

Packt

11 Feb 2014

10 min read

Introduction to vSphere Distributed switches

Packt

11 Feb 2014

10 min read

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7980

Packt

10 Feb 2014

8 min read

XamChat – a Cross-platform App

Packt

10 Feb 2014

8 min read

(For more resources related to this topic, see here.) Describing our sample application concept The concept is simple: a chat application that uses a standard Internet connection as an alternative to sending text messages. There are several popular applications like this in the Apple App Store, probably due to the cost of text messaging and support for devices such as the iPod Touch or iPad. This should be a neat real-world example that could be useful for users, and will cover specific topics in developing applications for iOS and Android. Before starting with the development, let's list the set of screens that we'll need: Login / sign up: This screen will include a standard login and sign-up process for the user List of conversations: This screen will include a button to start a new conversation List of friends: This screen will provide a way to add new friends when we start a new conversation Conversation: This screen will have a list of messages between you and another user, and an option to reply A quick wireframe layout of the application would help us grasp a better understanding of the layout of the app. The following figure shows the set of screens to be included in your app: Developing our model layer Since we have a good idea of what the application is, the next step is to develop the business objects or model layer of this application. Let's start out by defining a few classes that would contain the data to be used throughout the app. It is recommended, for the sake of organization, to add these to a Models folder in your project. Let's begin with a class representing a user. The class can be created as follows: public class User { public int Id { get; set; } public string Username { get; set; } public string Password { get; set; } } Pretty straightforward so far; let's move on to create classes representing a conversation and a message as follows: public class Conversation { public int Id { get; set; } public int UserId { get; set; } public string Username { get; set; } } public class Message { public int Id { get; set; } public int ConversationId { get; set; } public int UserId { get; set; } public string Username { get; set; } public string Text { get; set; } } Notice that we are using integers as identifiers for the various objects. UserId is the value that would be set by the application to change the user that the object is associated with. Now let's go ahead and set up our solution by performing the following steps: Start by creating a new solution and a new C# Library project. Name the project as XamChat.Core and the solution as XamChat. Next, let's set the library to a Mono / .NET 4.5 project. This setting is found in the project option dialog under Build | General | Target Framework. You could also choose to use Portable Library for this project, Writing a mock web service Many times when developing a mobile application, you may need to begin the development of your application before the real backend web service is available. To prevent the development from halting entirely, a good approach would be to develop a mock version of the service. First, let's break down the operations our app will perform against a web server. The operations are as follows: Log in with a username and password. Register a new account. Get the user's list of friends. Add friends by their usernames. Get a list of the existing conversations for the user. Get a list of messages in a conversation. Send a message. Now let's define an interface that offers a method for each scenario. The interface is as follows: public interface IWebService { Task<User> Login(string username, string password); Task<User> Register(User user); Task<User[]> GetFriends(int userId); Task<User> AddFriend(int userId, string username); Task<Conversation[]> GetConversations(int userId); Task<Message[]> GetMessages(int conversationId); Task<Message> SendMessage(Message message); } As you see, we're using asynchronous communication with the TPL(Task Parallel Library) technology. Since communicating with a web service can be a lengthy process, it is always a good idea to use the Task<T> class for these operations. Otherwise, you could inadvertently run a lengthy task on the user interface thread, which would prevent user inputs during the operation. Task is definitely needed for web requests, since users could easily be using a cellular Internet connection on iOS and Android, and it will give us the ability to use the async and await keywords down the road. Now let's implement a fake service that implements this interface. Place classes such as FakeWebService in the Fakes folder of the project. Let's start with the class declaration and the first method of the interface: public class FakeWebService { public int SleepDuration { get; set; } public FakeWebService() { SleepDuration = 1; } private Task Sleep() { return Task.Delay(SleepDuration); } public async Task<User> Login( string username, string password) { await Sleep(); return new User { Id = 1, Username = username }; } } We started off with a SleepDuration property to store a number in milliseconds. This is used to simulate an interaction with a web server, which can take some time. It is also useful for changing the SleepDuration value in different situations. For example, you might want to set this to a small number when writing unit tests so that the tests execute quickly. Next, we implemented a simple Sleep method to return a task that introduce delays of a number of milliseconds. This method will be used throughout the fake service to cause a delay on each operation. Finally, the Login method merely used an await call on the Sleep method and returned a new User object with the appropriate Username. For now, any username or password combination will work; however, you may wish to write some code here to check specific credentials. Now, let's implement a few more methods to continue our FakeWebService class as follows: public async Task<User> Register(User user) { await Sleep(); return user; } public async Task<User[]> GetFriends(int userId) { await Sleep(); return new[] { new User { Id = 2, Username = "bobama" }, new User { Id = 2, Username = "bobloblaw" }, new User { Id = 3, Username = "gmichael" }, }; } public async Task<User> AddFriend( int userId, string username) { await Sleep(); return new User { Id = 4, Username = username }; } For each of these methods, we kept in mind exactly same pattern as the Login method. Each method will delay and return some sample data. Feel free to mix the data with your own values. Now, let's implement the GetConversations method required by the interface as follows: public async Task<Conversation[]> GetConversations(int userId) { await Sleep(); return new[] { new Conversation { Id = 1, UserId = 2 }, new Conversation { Id = 1, UserId = 3 }, new Conversation { Id = 1, UserId = 4 }, }; } Basically, we just create a new array of the Conversation objects with arbitrary IDs. We also make sure to match up the UserId values with the IDs we've used on the User objects so far. Next, let's implement GetMessages to retrieve a list of messages as follows: public async Task<Message[]> GetMessages(int conversationId) { await Sleep(); return new[] { new Message { Id = 1, ConversationId = conversationId, UserId = 2, Text = "Hey", }, new Message { Id = 2, ConversationId = conversationId, UserId = 1, Text = "What's Up?", }, new Message { Id = 3, ConversationId = conversationId, UserId = 2, Text = "Have you seen that new movie?", }, new Message { Id = 4, ConversationId = conversationId, UserId = 1, Text = "It's great!", }, }; } Once again, we are adding some arbitrary data here, and mainly making sure that UserId and ConversationId match our existing data so far. And finally, we will write one more method to send a message as follows: public async Task<Message> SendMessage(Message message) { await Sleep(); return message; } Most of these methods are very straightforward. Note that the service doesn't have to work perfectly; it should merely complete each operation successfully with a delay. Each method should also return test data of some kind to be displayed in the UI. This will give us the ability to implement our iOS and Android applications while filling in the web service later. Next, we need to implement a simple interface for persisting application settings. Let's define an interface named ISettings as follows: public interface ISettings { User User { get; set; } void Save(); } Note that you might want to set up the Save method to be asynchronous and return Task if you plan on storing settings in the cloud. We don't really need this with our application since we will only be saving our settings locally. Later on, we'll implement this interface on each platform using Android and iOS APIs. For now, let's just implement a fake version that will be used later when we write unit tests. The interface is created by the following lines of code: public class FakeSettings : ISettings { public User User { get; set; } public void Save() { } } Note that the fake version doesn't actually need to do anything; we just need to provide a class that will implement the interface and not throw any unexpected errors. This completes the Model layer of the application. Here is a final class diagram of what we have implemented so far:

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4578

Packt

06 Feb 2014

6 min read

Bitcoins – Pools and Mining

Packt

06 Feb 2014

6 min read

(For more resources related to this topic, see here.) Installing Bitcoind Bitcoind is the software that connects you to other nodes in the network. There is no single point of failure, and the more nodes there are the faster and more secure the network becomes. Peers are rewarded with a transaction fee for the first validation of a transaction and are assigned randomly. After installing Bitcoind by using the following command, we have to synchronize it with the network, which means downloading millions of transactions exceeding a gigabyte in size to your Pi. sudo apt-get install bitcoind Before running the background daemon, you need to consider changing the data directory as the database files can take up many gigabytes of space. Mount a new storage place and always start Bitcoind with the following line: bitcoind –datadir /mnt/HDD/bitcoin –daemon After a few minutes, you can type in the following basic commands. You will need to wait until the entire block chain data is downloaded before you can do anything useful. During this time, the Pi might become less responsive, use a lot of bandwidth, and create a large amount of data in the data directory. This can take up to 12 hours. bitcoind getinfobitcoind getblockcount If you already have most of the block chain data downloaded on another computer, you can just copy all the data to the Pi. You can even have the same wallet and addresses in both locations. It is not recommended though, as that means it's twice as easy for hackers to get your wallet. Always encrypt your wallet with a very strong password and keep the password and wallet backup in a safe, offline place—like CDs or USB drives. If you lose the password, you lose access to the wallet, forever. Bitcoin wallet You need to generate addresses where other people can send you funds. Theoretically, you can generate an unlimited number of addresses, but practically managing all those addresses would become difficult. Bitcoin, by default, allows you to have a hundred addresses. You always get a default wallet address, which counts as the first address, and this address will receive network fees if you process any transactions for the first time. Cryptocurrency transactions cannot be reversed. Sending coins to the incorrect address means your coins will be lost forever. On the other hand, it also protects you if you are receiving coins from somebody else, as they cannot reverse the transaction. These addresses are globally unique, and can never be generated by anybody else in the universe or beyond it. It can get stolen by hackers or viruses, though. Imagine losing your wallet in real life. Unless a kind person returns it to you, the contents of that wallet will be lost forever. You can back up your wallet file, but you should store it on any two USB flash drives or CDs, and store it in a safety deposit box at home or in the bank. You should never be tempted to copy your wallet to any kind of online storage or backup services, especially if it's unencrypted. Creating a Bitcoin address These examples will work with the command line, as you can re-use them to display data on your web server. All online wallets use the Bitcoind API to generate addresses and manage your wallet. As a word of warning, you should never use online wallet services as almost all of them have been hacked, resulting in massive numbers of coins getting stolen. You can download the Bitcoin-QT client and run it in X if you prefer an easy way to manage your wallet. The following command lines will create a new receiving address and then list all your addresses: bitcoind getnewaddressbitcoind listaccounts Receiving Bitcoins As long as you know your address, people can send you Bitcoins. You do not need to have Bitcoind running all the time as the transactions are processes and are stored in the network. It is just very important to keep a backup of your wallet.dat file if you want to send the Bitcoins somewhere else, like an online exchange. Sending Bitcoins As long as you have coins in your wallet, you can easily send coins to another address by using the sendtoaddress command followed by the address and the amount. Here is an example sending 0.01 Bitcoins to the author's tip jar: bitcoind sendtoaddress 126HA8L1dP7fr7ECu2oEMtz6JpDRnzqp9N 0.01 You will get a response, which is a transaction ID. If you do not, the transaction has failed. You need to have at least 0.0001 Bitcoins reserved for the transaction fees. If you are sending large amounts of coins, this transaction fee will also become more expensive. The value of Bitcoins In July 2010, the value of Bitcoin was below 1 USD. Investing in Bitcoins was very controversial and a huge risk, since it was difficult to predict if the currency would be accepted or rejected by the community. As of writing this article, the Bitcoin value has exceeded 1100 USD. You can search the Internet and find interesting articles on early adopters mining Bitcoins, or buying a few hundred dollars and leaving their wallets lying around. Just like one person in the UK who threw away his hard drive with 7500 BTC stored on it. After going public, thousands of people flocked to the public dump ground to search for the hard drive. Other stories include a student who invested a few hundred dollars in 2010, and sold them for hundreds of thousands of dollars. With such large amounts, it is important to consult your local TAX authority or council. The trend seems to be that the more people find out about Bitcoins and the more media publicity it gets, the higher the value of the currency rises. This also looks like it applies to alternative currencies such as Litecoin. Summary We have seen what Bitcoin is. We have seen what are the uses of Bitcoins and also it's value. We have also seen how to send and receive Bitcoins. I hope this has given you a better idea about what Bitcoins really are. Resources for Article: Further resources on this subject: Clusters, Parallel Computing, and Raspberry Pi – A Brief Background [Article] Creating a file server (Samba) [Article] Our First Project – A Basic Thermometer [Article]

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21068

How-To Tutorials

article-image-article-managing_your_social_channels

Packt

28 Jan 2014

3 min read

Managing your social channels

Packt

28 Jan 2014

3 min read

(For more resources related to this topic, see here.) Targeted traffic is the lifeline of any website or blog. Most people rely on search engines for their traffic; but, when your social media channels are optimized properly, they can drive a huge amount of targeted traffic to your website or blog. Getting ready Blogs came way before Facebook, Twitter, and Google+, and they're still going strong. Every time you blog, you get a chance to get another one of your pages indexed by Google. Let's have a look at how we can use the Blog tool provided by HubSpot. How to do it... Make sure the title of your blog contains the relevant keywords. Now, in the Content tab, select Blog from the drop-down list as shown in the following screenshot: Now, select the Create Article option, which is located right under the Using the HubSpot Blog section, as shown in the following screenshot: If you look at the right-hand side of your browser now, HubSpot will be trying to help you out by displaying the important elements that are missing from the blog. Start filling in all those elements one-by-one. Enter your keyword-rich blog title in the textbox named Title and your content in the text area named Article Body. A blog should contain no fewer than 500 words. Use the options Bold, Italic, and Underline whenever required. Avoid writing a full-length essay. Try to use subheadings, numbers, and bullets. An image can speak a thousand words. Make sure you insert a relevant image for your blog, as images have the ability to drive decent traffic to your blog or website. Don't forget to give a relevant name and alt text attribute for the image you attach along with the keywords you identified. You can also select the option Left, Right, or Center depending upon where you want the image to be displayed in your blog. Make sure the tags you add are relevant to the blog. Tags are generally used in a blog to make it easier for the reader to identify the topic they are looking for. Once you are done with the tags, click on the Publish button to make your blog go live as shown in the following screenshot: Summary In this article we learned about using a Blog tool provided by HubSpot to manage our social channel. Resources for Article: Further resources on this subject: Clojure for Domain-specific Languages - Design Concepts with Clojure [Article] Cross-browser-distributed testing [Article] Working with Dashboards in Dynamics CRM [Article]

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1446

How-To Tutorials

Packt

27 Jan 2014

5 min read

Understanding Citrix®Provisioning Services 7.0

Packt

27 Jan 2014

5 min read

0
0
4746

article-image-diagnostic-leveraging-accelerated-poc-crm-online-service

Packt

24 Jan 2014

16 min read

Diagnostic leveraging of the Accelerated POC with the CRM Online service

Packt

24 Jan 2014

16 min read

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1705

article-image-improving-proximity-filtering-knn

Packt

24 Jan 2014

7 min read

Improving proximity filtering with KNN

Packt

24 Jan 2014

7 min read

(For more resources related to this topic, see here.) The basic question that we seek to answer in this article is the fundamental distance question, "Which are the closest (name what you are searching for) to me?", for example, "Which are the five coffee shops closest to me?" It turns out that while it is a fundamental question, it's not always easy to answer, though we will make this possible in this article. We will approach this with two approaches. The first way in which we'll approach this is in a simple heuristic, which will allow us to come to a solution quickly. Then, we'll take advantage of the deeper PostGIS functionality to make the solution faster and more general with a K-Nearest Neighbor (KNN) approach. A concept that we need to understand from the outset is that of a spatial index. A spatial index, like other database indexes, functions like a book index. It is a special construct to make looking for things inside our table easier, much in the way a book index helps us find content in a book faster. In the case of a spatial index, it helps us find faster where things are in space. Therefore, by using a spatial index in our geographic searches, we can speed up our searches by many orders of magnitude. To learn more about spatial indexes, see http://en.wikipedia.org/wiki/Spatial_index#Spatial_index. Getting ready We will start by loading our data. Our data are the address records from Cuyahoga County, Ohio, USA. shp2pgsql -s 3734 -d -i -I -W LATIN1 -g the_geom CUY_ADDRESS_POINTS chp04.knn_addresses | psql -U me -d postgis_cookbook As this dataset may take a while to load, you can alternatively load a subset. shp2pgsql -s 3734 -d -i -I -W LATIN1 -g the_geom CUY_ADDRESS_POINTS_ subset chp04.knn_addresses | psql -U me -d postgis_cookbook We specified the -I flag in order to request a spatial index be created upon the import of this data. Let us start by seeing how many records we are dealing with: SELECT COUNT(*) FROM chp04.knn_addresses; --484958 We have, in this address table, almost half a million address records, which is not an insubstantial number against which to perform a query. How to do it... KNN is an approach to searching for an arbitrary number of points closest to a given point. Without the right tools, this can be a very slow process that requires testing the distance between the point of interest and all the possible neighbors. The problem with this approach is that the search becomes exponentially slower as the number of points increases. Let's start with this naïve approach and then improve upon it. Suppose we were interested in finding 10 records closest to the geographic location, -81.738624, 41.396679. The naïve approach would be to transform this value into our local coordinate system and compare the distance to each point in the database from the search point, order those values by distance, and limit the search to the first 10 closest records (it is not recommended that you run the following query—it could run indefinitely) SELECT ST_Distance(searchpoint.the_geom, addr.the_geom) AS dist, * FROM chp04.knn_addresses addr, (SELECT ST_Transform(ST_SetSRID(ST_MakePoint(-81.738624, 41.396679), 4326), 3734) AS the_geom) searchpoint ORDER BY ST_Distance(searchpoint.the_geom, addr.the_geom) LIMIT 10; This is a fine approach for smaller datasets. This is a logical, simple, fast approach for relatively small numbers of records. This approach scales very poorly, however, getting exponentially slower with the addition of records, and with 500,000 points, this would take a very long time. An alternative is to only compare my point to the ones I know are close by setting a search distance. So, for example, in the following diagram, we have a star that represents my current location, and I want to know the 10 closest addresses. The grid in the diagram is a 100 foot grid, so I can search for the points within 200 feet, then measure the distance to each of these points, and return the closest 10 points to my search location. So far, our approach to answering this question is to limit the search using the ST_DWithin operator to only search for records within a certain distance. ST_DWithin uses our spatial index, so the initial distance search is fast and the list of returned records should be short enough to do the same pair-wise distance comparison we did earlier in this section. In our case here, we could limit the search to within 200 feet as follows. SELECT ST_Distance(searchpoint.the_geom, addr.the_geom) AS dist, * FROM chp04.knn_addresses addr, (SELECT ST_Transform(ST_SetSRID(ST_MakePoint(-81.738624, 41.396679), 4326), 3734) AS the_geom) searchpoint WHERE ST_DWithin(searchpoint.the_geom, addr.the_geom, 200) ORDER BY ST_Distance(searchpoint.the_geom, addr.the_geom) LIMIT 10; This approach performs well so long as our search window, ST_DWithin, is the right size for the data. The problem with this approach is that, in order to optimize it, we need to know how to set a search window that is about the right size. Any larger than the right size and the query will run more slowly than we'd like. Any smaller than the right size and we might not get all the points back that we need. Inherently, we don't know this ahead of time, so we can only hope for the best guess. In this same dataset, if we apply the same query in another location, the output will return no points because the 10 closest points are further than 200 feet away. We can see this in the following diagram: Fortunately, for PostGIS 2.0, we can leverage the distance operators (<-> and <#>) to do indexed nearest-neighbor searches. This makes for very fast KNN searches that don't require us to guess ahead of time how far away we need to search. Why are the searches fast? The spatial index helps, of course, but in the case of the distance operator, we are using the structure of the index itself, which is hierarchical, to very quickly sort our neighbors. When used in an ORDER BY clause, the distance operator uses the index: SELECT ST_Distance(searchpoint.the_geom, addr.the_geom) AS dist, * FROM chp04.knn_addresses addr, (SELECT ST_Transform(ST_SetSRID(ST_MakePoint(-81.738624, 41.396679), 4326), 3734) AS the_geom) searchpoint ORDER BY addr.the_geom <-> searchpoint.the_geom LIMIT 10; This approach requires no a priori knowledge of how far the nearest neighbors might be. It also scales very well, returning thousands of records in not more than the time it takes to return a few records. It is sometimes slower than using ST_DWithin, depending on how small our search distance is and how large the dataset we are dealing with. But the tradeoff is that we don't need to make a guess as to our correct search distance and for large queries, it can be much faster than the naïve approach. How it works... What makes this magic possible is that PostGIS uses an R-Tree index. This means that the index itself is sorted hierarchically based on spatial information. As demonstrated, we can leverage the structure of the index in sorting distances from a given arbitrary location and, thus, use the index to directly return the sorted records. This means that the structure of the spatial index itself helps us answer such fundamental questions quickly and inexpensively. More information about KNN and R-tree can be found at http://workshops.boundlessgeo.com/postgis-intro/knn.html and https://en.wikipedia.org/wiki/R-tree. Summary This article covered the introduction and learning of KNN filters to increase the performance of proximity queries. Now you must be quite familiar with the usage of KNN filters to increase the performance of proximity queries. Resources for Article: Further resources on this subject: PostgreSQL: Tips and Tricks [article] Backup in PostgreSQL 9 [article] Python Libraries for Geospatial Development [article]

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2315

article-image-good-time-management-casperjs-tests

Packt

24 Jan 2014

5 min read

Good time management in CasperJS tests

Packt

24 Jan 2014

5 min read

(For more resources related to this topic, see here.) When developing with JavaScript, we often need to chain two pieces of code (for instance, first we load some JSON data, and then we update the page content using that data). But each step is generally non-blocking (meaning the rest of the code will continue to execute even if the step is not complete), and there is no way to predict when the first step will be complete. The most solid and most common approach to solve this problem is the callback mechanism. We put the second piece of code in a function, and pass it as a parameter to the first one, so that it can call this function when it finishes. As a result, there is no linear and predictably-ordered execution of the code, which makes testing a little bit tricky. The following is an example. Use case – simple place name matching with Geonames.org <html> <head> <script type='text/javascript' src = 'http://code.jquery.com/jquery-1.9.1.js'></script> <style> .searching { color: grey;} .success { color: green;} .noresults {color: red;} </style> </head> <body> <script> function geonamesSearch() { $('#results').html("Searching..."); $('#results').attr('class', 'searching'); var url = "http://ws.geonames.org/searchJSON"; var query = $('#searchedlocation').val(); $.getJSON(url + "?q="+ query +"&maxRows=25&featureClass=P", null, function(data) { var data = data.geonames; var names = []; if(data.length > 0) { $.each(data, function(i, val){ names.push(val.name +" ("+val.adminName1+")"); }); $('#results').html(names.join("<br/>")); $('#results').attr('class', 'success'); } else { $('#results').html("No matching place."); $('#results').attr('class', 'noresults'); } } ); } </script> <input type="text" id="searchedlocation" /> <button id="search" onclick="geonamesSearch();">Click me</button> <div id="results"></div> </body> </html> This page contains a text input field, a button, and an empty div whose ID is 'results'. When we click on the button, the JavaScript function geonamesSearch does the following: It puts the 'searching' class on the results div, and inserts the mention Searching... It reads the current value of the text input It calls the Geonames.org JSON web services to get the place names matching this value This JSON call is performed by jQuery and we provides it with a callback function (that will be called when the Geonames web service will respond), which reads the results If there is no result, it changes the results div class to 'noresults', and its text to No matching place. If there are some results, it sets the class to 'success' and displays the matching place names. We can try it with our web browser, and see it works nicely. Testing our use case with CasperJS Now let's test this page with the following CasperJS script which enters the value 'barcelona' and asserts we do get Barcelona (Catalonia) in the results: casper.userAgent('Mozilla/5.0 (Macintosh; Intel Mac OS X)'); casper.test.begin('Search a city by name', 1, function(test) { casper.start('http://localhost:8000/example3.html', function() { this.sendKeys("input#searchedlocation", "barcelona"); this.click("button#search"); }); casper.then(function() { test.assertTextExists('Barcelona (Catalonia)', 'Barcelona (Catalonia) has been found.'); }) casper.run(function() { test.done(); }); }); Note that we need to set up a regular user agent to make sure geonames.org will accept to process our request. If we run it, we get a failure: Why is that? It is because our this.click() triggers the geonamesSearch function and immediately after we try to assert the result content, but the Geonames web service had no enough time to respond, the content is not yet the one expected at the time the assertion is performed. Timing is everything The CasperJS then() blocks allow to make sure we will execute our test steps sequence in the right order, but they cannot guarantee that an asynchronous call performed in one of the block will be complete before we move to the next block. To manage this kind of cases, CasperJS offers the ability to wait before executing the rest of our test sequence. Here is a working test script: casper.userAgent('Mozilla/5.0 (Macintosh; Intel Mac OS X)'); casper.test.begin('Search a city by name', 1, function(test) { casper.start('http://localhost:8000/example3.html', function() { this.sendKeys("input#searchedlocation", "barcelona"); this.click("button#search"); }); casper.waitForSelector('div.success', function() { test.assertTextExists('Barcelona (Catalonia)', 'Barcelona (Catalonia) has been found.'); }) casper.run(function() { test.done(); }); }); We can see the tests pass successfully now: With waitForSelector, we make sure the assertion will be performed only when the results div will have the 'success' class, and it will only happen once our JSON loading callback function has been called. Summary In this article, we learned how to test our use case with CasperJS and how timing is everything. Resources for Article: Further resources on this subject: Introducing a feature of IntroJs [article] So, what is Ext JS? [article] So, what is EaselJS? [article]

0
0
1958

Packt

23 Jan 2014

19 min read

The Design Documentation

Packt

23 Jan 2014

19 min read

0
2
47263

Packt

23 Jan 2014

6 min read

XenApp® Policies

Packt

23 Jan 2014

6 min read

(For more resources related to this topic, see here.) Creating a XenApp® Computer or User policy This recipe will show you how to create policies in general to configure Computer and User settings for Citrix XenApp. Getting ready Before configuring computer and user policies, you have to decide which tool to use to create and configure Citrix policies. As of Citrix XenApp 6.x, you can use both the Microsoft Group Policy Management Console (GPMC) as Citrix's AppCenter to create policies. Policies can be managed from only one of the consoles as policies created with GPMC are not visible in AppCenter and vice versa. When using GPMC, a public hotfix must be installed on the machine that is running on the management console. The latest version can be found at Citrix's Knowledge Center: http://support.citrix.com/product/xa/v6.5_2008r2/hotfix/general/public/. How to do it... To create a Citrix policy that is applied to the XenApp servers with AppCenter, follow these steps: Open the Citrix XenApp Management Console AppCenter (Start | Administrative Tools | Citrix | Management Consoles). Navigate to XenApp | <FarmName> | Policies in the left pane. Click on the Computer tab in the Policies pane. Click on New to create a new policy. Enter values in the Name and Description fields for the policy and click on Next. Select a category in the left pane. Add a policy setting by clicking on Add in the right pane for each setting. Configure the policy setting and click on OK. Repeat steps 6 to 8 to add more policy settings. Click on Next when all policy settings are configured. Configure the filter settings and click on Next. The filter options are addressed in the next recipe. Ensure the Enable this policy option is selected and click on Create. Computer policies are applied to XenApp servers when the server is started or when policy updates are applied to the XenApp server. To force the policies to be applied immediately to the XenApp server, run the following command on the server: gpupdate /force To create a Citrix policy that is applied to the XenApp user session with AppCenter, follow these steps: Open the Citrix XenApp management console AppCenter (Start | Administrative Tools | Citrix | Management Consoles). Navigate to XenApp | <FarmName> | Policies in the left pane. Click on the User tab in the Policies pane. Click on New to create a new policy. Enter values in the Name and Description fields for the policy and click on Next. Select a category in the left pane. Add a policy setting by clicking on Add in the right pane for each setting. Configure the policy setting and click on OK. Repeat steps 6 to 8 to add more policy settings. Click on Next when all policy settings are configured. Configure the filter settings and click on Next. Filter options are addressed in the next recipe. Ensure the Enable this policy option is selected and click on Create. Just like Windows User policies, Citrix User policies are applied when the user session starts. There's more... You can read more on creating Citrix policies at Citrix's eDocs at http://support.citrix.com/proddocs/topic/xenapp65-admin/ps-admin-publishing-policies-create-all.html. See also The Adding filters to a policy recipe The Comparing XenApp® policies and templates recipe The Simulating connection scenario's with Citrix® policies recipe The Configuring policy priorities and exceptions recipe Adding filters to a policy This recipe will show you how to add filters to a policy to apply the policy to a selective group of XenApp servers or user sessions. Policies that are not configured with a filter apply to all XenApp servers in the farm and to all logged on users for a XenApp session. This will have the same effect as using the default unfiltered computer or user policy that cannot have a filter applied to it. How to do it... You can apply different policy filters to computer or user policies. To add filters to a Citrix Computer policy follow these steps: Create a new policy by following steps 1 to 10 from the previous recipe. Click on Add to configure the Organizational Unit (OU) or Worker Group filter. Click on Add to configure a filter element. Configure the mode (allow or deny) and use Browse to find the correct worker group or OU. Click on OK to add the filter element. Repeat steps 3 to 5 to add more filter elements. Click on OK to add the filter to the policy. Repeat steps 2 to 7 to configure multiple filters for the policy. Click on Next. Ensure the Enable this policy option is selected and click on Create. To add filters to a Citrix User policy follow these steps: Create a new policy by following the steps 1 to 10 from the previous recipe. Click on Add to configure Access Control, Branch Repeater, Client IP Address, Client Name, Organizational Unit (OU), User or Group, or Worker Group filter. Click on Add to configure a filter element. Configure the mode (allow or deny) and use Browse to find the correct OU, User or Group, or Worker Group, or enter filter-specific settings for Client IP Address, Name, Access Control, or Branch Repeater. Click on OK to add the filter element. Repeat steps 3 to 5 to add more filter elements. Click on OK to add the filter to the policy. Repeat steps 2 to 7 to configure multiple filters for the policy. Click on Next. Ensure the Enable this policy option is selected and click on Create. See also The Creating a XenApp® Computer or User policy recipe The Comparing XenApp® policies and templates recipe The Simulating connection scenarios with Citrix® policies recipe The Configuring policy priorities and exceptions recipe Comparing XenApp® policies and templates This recipe will show you how to compare policy settings with other policies or policy templates by using Citrix's management console AppCenter to see if policies contain similar settings, contradicting settings, or have no correlation whatsoever. How to do it... To compare policies with templates in AppCenter, follow these steps: Open the Citrix XenApp management console AppCenter (Start | Administrative Tools | Citrix | Management Consoles). Navigate to XenApp | <FarmName> | Policies in the left pane. Click on the Templates tab in the Policies pane. Click on the Compare View icon on the right-hand side of the menu bar. Select the policies that you want to compare and click on Compare. To check the configured policy settings against default policy settings for the XenApp Farm, select a policy, and select the Compare to setting defaults option. The policy settings from the selected policies are shown and can easily be compared. To add additional policies to the comparison or check all available policy settings, click on Configured Settings and select either Add/Remove Columns or Show All Settings. There's more... You can read more about comparing policies and templates at Citrix's eDocs: http://support.citrix.com/proddocs/topic/xenapp65-admin/ps-policies-templates-compare.html. See also The Creating a XenApp® Computer or User policy recipe The Adding filters to a policy recipe The Simulating connection scenarios with Citrix® policies recipe The Configuring policy priorities and exceptions recipe

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3032

article-image-branding-sharepoint-device-channels-and-design-packages

Packt

22 Jan 2014

11 min read

Branding SharePoint with Device Channels and Design Packages

Packt

22 Jan 2014

11 min read

With the 2013 release of SharePoint, Microsoft has added two new capabilities that assist with full-scale branding of SharePoint sites: device channels and design packages. A device channel uses the user agent of the web browser sending the incoming web request to determine which master page to render the content pages with. A common use of the device channels is to detect tablets and smartphones to use a more touch-friendly interface design. For instance, a device channel can be configured to look for an iPad in the following user agent to identify the iPad devices: Mozilla/5.0 (iPad; CPU OS 7_0_4 like Mac OS X)AppleWebKit/537.51.1 (KHTML, like Gecko) Version/7.0Mobile/11B554a Safari/9537.53 Any portion of the user agent can be used for a device channel. It is important to be specific, but not too specific. Using iPad would apply to all the devices that specify iPad in their user agent, whereas iPad; U; CPU OS 7_0 would only apply to iPads running on iOS Version 7.0. A design package is a SharePoint solution, packaged as a WSP file containing branding customizations, such as master pages and cascading style sheets. This provides a simple method of exporting a site design from one site and applying it to another. A design package will only contain items that are not default to SharePoint. Default items, such as the included master pages, will be referenced, but are not included as part of the package. Prior to SharePoint 2013, packaged design solutions could only be created manually or with Visual Studio. Design packages allow any site collection administrator to create and apply packaged designs. This allows the site collection administrators to obtain packaged designs (from third parties, and so on) and apply them, without having to manually upload and configure each piece of the design. Creating a device channel for mobile devices One of the most common scenarios for using device channels is to identify the tablet and smartphone browsers. Applying a mobile-specific master page, when appropriate, can provide the users with a design that is more touch friendly and is laid out in a specific manner for smaller screens. In this recipe, we are going to create a device channel that will identify Android, iOS, BlackBerry, WebOS, and Windows mobile devices. There are hundreds of mobile-specific browsers that we can detect with the user agent. However, for this recipe we are going to keep it simple. Getting ready In order to view and modify the device channels for a SharePoint site, the SharePoint Server Publishing Infrastructure site collection feature and SharePoint Server Publishing site feature must be activated. How to do it... Follow these steps to create a device channel for mobile devices: Navigate to the site in your preferred web browser. Select Site settings from the Settings menu. Select Device Channels from the Look and Feel section. You can also navigate to the Device Channels page from the Design Manager page. Select New Item. Provide a Name, Description, and Alias for the device channel. The Alias field specified will be used when specifying which master page to use with the device channel in the device channel mappings file. We will learn about this in the next recipe, Applying a master page to a device channel. Specify the Device Inclusion Rules to be included in the device channel. Android iPad iPod iPhone BlackBerry IEMobile WebOS When using multiple device inclusion rules, place each string on a new line to match the user agent. Device Inclusion Rules are simply strings that are looked for in the user agent of incoming web requests. Mark the Active checkbox and click on Save. How it works... Device channels are created and stored in the /DeviceChannels SharePoint list in the root site of a site collection. When an incoming browser request is received, SharePoint checks whether the incoming user agent matches any of the Device Inclusion Rules before selecting the master page to use. Many web browsers have developer tools that allow changing the user agent reported by the browser. Switching the user agent is one way in which we can test to ensure our device channels are working correctly. Internet Explorer 11, for instance, includes this option in the Emulation section of the F12 Developer Tools. There's more... A device channel may also be created with PowerShell or with code using the server-side object model. Creating a device channel for mobile devices using PowerShell Follow these steps to create a device channel for mobile devices using PowerShell: Get the site using the Get-SPWeb Cmdlet. $web = Get-SPWeb http://sharepoint/site Get the DeviceChannels list. $list = $web.Lists["Device Channels"] Add a new SPListItem item to the Items collection of the list. $item = $list.Items.Add() Assign the values to each of the properties on the SPListItem item. $item["Name"] = "PowerShell" $item["Alias"] = "PowerShell" $item["Description"] = "PowerShell Channel" $item["Device Inclusion Rules"] = "Android`niPad`niPod`niPhone`nBlackBerry`nIEMobile`nWebOS" $item["Active"] = $true When a line break is required within a string, in PowerShell, an escape character can be used. Escape characters in PowerShell use the tilde character. For example, a new line is represented by `n. Call the Update method on the list to update the Items collection. $item.Update() Use the Dispose method to discard the SPWeb object. $web.Dispose() Creating a device channel for mobile devices with code using the server-side object model Follow these steps to create a device channel for mobile devices with code using the server-side object model: Open the site collection containing the site in a using statement. using (var site = new SPSite("http://sharepoint/site")) Open the site in a using statement. using (var web = site.OpenWeb()) Get the DeviceChannels list. var list = web.Lists["Device Channels"]; Add a new SPListItem item to the Items collection of the list. var item = list.Items.Add(); Assign the values to each of the properties on the SPListItem item. item["Name"] = "Code"; item["Alias"] = "Code "; item["Description"] = "Code Channel"; item["Device Inclusion Rules"] = "AndroidniPadniPodniPhonenBlackBerrynIEMobilenWebOS"; item["Active"] = true; When a line break is required within a string in C#, an escape character can be used. Escape characters in C# use the backslash character. For example, a new line is represented by n. Call the Update method on the list to update the Items collection. item.Update(); See also SharePoint Design Manager branding and design capabilities How to: Add or Delete List Items SPWeb class SPSite class Get-SPWeb Applying a master page to a device channel Once a device channel has been created, it can be configured to use as a different site master page rather than the default site master page. For instance, browsers targeted by a mobile device channel could display the content using the oslo master page whereas all other browsers could display the same content using the seattle master page. The System Master Page is configured for all device channels and cannot be configured for individual device channels. How to do it... Follow these steps to apply a master page to a device channel: Navigate to the site in your preferred web browser. Select Site settings from the Settings menu. Select Master page from the Look and Feel section. Specify which Site Master Page to use for each device channel. Click on Save. How it works... The master page to device channel mappings are stored in the _catalogs/masterpages/__DeviceChannelMappings.aspx file as XML within the root site of a site collection. For each incoming browser web request, this file is used by SharePoint to determine which master page to use with the content returned to the browser. There's more... A device channel mapping may also be configured with PowerShell or with code using the server-side object model. In this recipe, these two methods are similar. However, the .NET reflection methods used are slightly different. When an object is instantiated with reflection in PowerShell, its public properties and methods become available to the command line. However, when an object is instantiated with reflection in the .NET code, each property and method needs to be searched for before being able to access them. The methods that provide the functionality to configure the device channel mappings are not publicly exposed in the SharePoint assemblies. As a result, we will use the .NET reflection to instantiate the objects required. It is important to note that non-public classes in the SharePoint assemblies can change between SharePoint versions and updates without notice. Using reflection tools, such as .NET Reflector (http://www.red-gate.com/products/dotnet-development/reflector/) and dotPeek (http://www.jetbrains.com/decompiler/), we can browse the assemblies to adjust the references accordingly. Applying a master page to a device channel using PowerShell Follow these steps to apply a master page to a device channel using PowerShell: Load the Microsoft.SharePoint.dll and Microsoft.SharePoint.Publishing.dll assemblies into the PowerShell session. [Reflection.Assembly]::LoadFrom("C:Program FilesCommonFilesmicrosoft sharedWeb ServerExtensions15ISAPIMicrosoft.SharePoint.Publishing.dll") [Reflection.Assembly]::LoadFrom("C:Program FilesCommonFilesmicrosoft sharedWeb ServerExtensions15ISAPIMicrosoft.SharePoint.dll") Get the object types for the parameters that will be used when getting the class constructor for the MasterPageMappingsFile object and later instantiating the object. $typeWeb = [Microsoft.SharePoint.SPWeb] $typeBool = [System.Boolean] $typeMappingFile =[System.Type]::GetType("Microsoft.SharePoint.Publishing.Mobile.MasterPageMappingsFile, Microsoft.SharePoint.Publishing,Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c") Create an array of the object types. $consMappingFileParams = ($typeWeb, $typeBool, $typeWeb) Get the class constructor for the MasterPageMappingsFile object. $consMappingFile = $typeMappingFile.GetConstructor($consMappingFileParams) Create an array of the parameters required to instantiate the MasterPageMappingsFile object. $mappingFileParams =[System.Array]::CreateInstance([System.Object], 3)$mappingFileParams[0] = (Get-SPSitehttp://sharepoint/sitecollection).RootWeb$mappingFileParams[1] = $false$mappingFileParams[2] = $null When invoking a constructor to create an instance of a .NET object in PowerShell, we have to create a System.Object array rather than using a PowerShell array. Even though the base class for a PowerShell array is System.Object[], when calling the Invoke method on the class constructor, it will see it as a PSObject object instead. The same goes for the SPWeb object we are passing as the first parameter. .NET will see the object as a PSObject object instead of a SPWeb object if we use Get-SPWeb. However, if we get the SPWeb object from the SPSite object, it will not get treated as a PSObject object. Invoke the class constructor to create an instance of the MasterPageMappingsFile object. $mappingFile = $consMappingFile.Invoke($mappingFileParams) Set the MasterPageUrl property for the device channel on the MasterPageMappingsFile object. $mappingFile["PowerShell"].MasterPageUrl = "/_catalogs/masterpage/oslo.master" Save the changes using the UpdateSingleChannel method. $mappingFile.UpdateSingleChannel("PowerShell") Applying a master page to a device channel with code using the server-side object model Follow these steps to apply a master page to a device channel with code using the server-side object model: A reference to the Microsoft.SharePoint.Publishing.dll assembly is required for this recipe. Get the site collection in a using statement. using (var site = new SPSite("http://sharepoint/sitecollection")) Get the root site of the site collection in a using statement. using (var web = site.RootWeb) Get the object type that will be used when getting the class constructor for the MasterPageMappingsFile object and later instantiating the object. MasterPageMappingsFile object and later instantiating the object.var typeMappingFile =Type.GetType("Microsoft.SharePoint.Publishing.Mobile.MasterPageMappingsFile, Microsoft.SharePoint.Publishing,Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c"); Get the class constructor for the MasterPageMappingsFile object. var consMappingFile =typeMappingFile.GetConstructor(new Type[] { typeof(SPWeb),typeof(bool), typeof(SPWeb) }); Invoke the constructor to create an instance of the MasterPageMappingsFile object. var mappingFile = consMappingFile.Invoke(new object[] { web, false, null }); Get the mappings field of the MasterPageMappingsFile object, and cast the field as an IDictionary. var mappings = (IDictionary)typeMappingFile.GetField("mappings",BindingFlags.Instance | BindingFlags.NonPublic).GetValue(mappingFile); Set the MasterPageUrl property for the device channel on the mappings field. mappings["PowerShell"].GetType().GetProperty("MasterPageUrl",BindingFlags.Instance |BindingFlags.Public).SetValue(mappings["PowerShell"],"/_catalogs/masterpage/seattle.master", null); Set the mappings field of the MasterPageMappingsFile object. typeMappingFile.GetField("mappings", BindingFlags.Instance |BindingFlags.NonPublic).SetValue(mappingFile, mappings); Get the UpdateSingleChannel method from the type of the MasterPageMappingsFile object. var updateMethod = typeMappingFile.GetMethod("UpdateSingleChannel",BindingFlags.Instance | BindingFlags.Public, null, new Type[]{ typeof(string) }, null); Save the changes by invoking the UpdateSingleChannel method. updateMethod.Invoke(mappingFile, new object[] { "Code" });

0
0
4767

article-image-organizing-backbone-applications-structure-optimize-and-deploy

Packt

21 Jan 2014

9 min read

Organizing Backbone Applications - Structure, Optimize, and Deploy

Packt

21 Jan 2014

9 min read

(For more resources related to this topic, see here.) Creating application architecture The essential premise at the heart of Backbone has always been to try and discover the minimal set of data-structuring (Models and Collections) and user interface (Views and URLs) primitives that are useful when building web applications with JavaScript. Jeremy Ashkenas, creator of Backbone.js, Underscore.js, and CoffeeScript As Jeremy mentioned, Backbone.js has no intention, at least in the near future, to raise its bar to provide application architecture. Backbone will continue to be a lightweight tool to produce the minimal features required for web development. So, should we blame Backbone.js for not including such functionality even though there is a huge demand for this in the developer community? Certainly not! Backbone.js only yields the set of components that are necessary to create the backbone of an application and gives us complete freedom to build the app architecture in whichever way we want. If working on a significantly large JavaScript application, remember to dedicate sufficient time to planning the underlying architecture that makes the most sense. It's often more complex than you may initially imagine. Addy Osmani, author of Patterns For Large-Scale JavaScript Application Architecture So, as we start digging into more detail on creating an application architecture, we are not going to talk about trivial applications or something similar to a to-do-list app. Rather, we will investigate how to structure a medium- or large-level application. After discussions with a number of developers, we found that the main issue they face here is that there are several methodologies the online blog posts and tutorials offer to structure an application. While most of these tutorials talk about good practices, it becomes difficult to choose exactly one from them. Keeping that in mind, we will explore a number of steps that you should follow to make your app robust and maintainable in the long run. Managing a project directory This is the first step towards creating a solid app architecture. We have already discussed this in detail in the previous sections. If you are comfortable using another directory layout, go ahead with it. The directory structure will not matter much if the rest of your application is organized properly. Organizing code with AMD We will use RequireJS for our project. As discussed earlier, it comes with a bunch of facilities such as the following: Adding a lot of script tags in one HTML file and managing all of the dependencies on your own may work for a medium-level project, but will gradually fail for a large-level project. Such a project may have thousands of lines of code; managing a code base of that size requires small modules to be defined in each individual file. With RequireJS, you do not need to worry about how many files you have—you just know that if the standard is followed properly, it is bound to work. The global namespace is never touched and you can freely give the best names to something that matches with it the most. Debugging the RequireJS modules is a lot easier than other approaches because you know what the dependencies and path to each of them are in every module definition. You can use r.js, an optimization tool for RequireJS that minifies all the JavaScript and CSS files, to create the production-ready build. Setting up an application For a Backbone app, there must be a centralized object that will hold together all the components of the application. In a simple application, most people generally just make the main router work as the central object. But that will surely not work for a large application and you need an Application object that should work as the parent component. This object should have a method (mostly init()) that will work as the entry point to your application and initialize the main router along with the Backbone history. In addition, either your Application class should extend Backbone.Events or it should include a property that points to an instance of the Backbone.Events class. The benefit of doing this is that the app or Backbone.Events instance can act as a central event aggregator, and you can trigger application-level events on it. A very basic Application class will look like the following code snippet: // File: application.js define([ 'underscore', 'backbone', 'router' ], function (_, Backbone, Router) { // the event aggregator var PubSub = _.extend({}, Backbone.Events); var Application = function () { // Do useful stuff here } _.extend(Application.prototype, { pubsub: new PubSub(), init: function () { Backbone.history.start(); } }); return Application; }); Application is a simple class with an init() method and a PubSub instance. The init() method acts as the starting point of the application and PubSub works as the application-level event manager. You can add more functionality to the Application class, such as starting and stopping modules and adding a region manager for view layout management. It is advisable to keep this class as short as you can. Using the module pattern We often see that intermediate-level developers find it a bit confusing to initially use a module-based architecture. It can be a little difficult for them to make the transition from a simple MVC architecture to a modular MVC architecture. While the points we are discussing in this article are valid for both these architectures, we should always prefer to use a modular concept in nontrivial applications for better maintainability and organization. In the directory structure section, we saw how the module consists of a main.js file, its views, models, and collections all together. The main.js file will define the module and have different methods to manage the other components of that module. It works as the starting point of the module. A simple main.js file will look like the following code: // File: main.js define([ 'app/modules/user/views/userlist', 'app/modules/user/views/userdetails' ], function (UserList, UserDetails) { var myVar; return { initialize: function () { this.showUserList(); }, showUsersList: function () { var userList = new UserList(); userList.show(); }, showUserDetails: function (userModel) { var userDetails = new UserDetails({ model: userModel }); userDetails.show(); } }; }); As you can see, the responsibility of this file is to initiate the module and manage the components of that module. We have to make sure that it handles only parent-level tasks; it shouldn't contain a method that one of its views should ideally have. The concept is not very complex, but you need to set it up properly in order to use it for a large application. You can even go for an existing app and module setup and integrate it with your Backbone app. For instance, Marionette provides an application infrastructure for Backbone apps. You can use its inbuilt Application and Module classes to structure your application. It also provides a general-purpose Controller class—something that doesn't come with the Backbone library but can be used as a mediator to provide generic methods and work as a common medium among the modules. You can also use AuraJS (https://github.com/aurajs/aura), a framework-agonistic event-driven architecture developed by Addy Osmani (http://addyosmani.com) and many others; it works quite well with Backbone.js. A thorough discussion on AuraJS is beyond the scope of this book, but you can grab a lot of useful information about it from its documentation and examples (https://github.com/aurajs/todomvc). It is an excellent boilerplate tool that gives your app a kick-start and we highly recommend it, especially if you are not using the Marionette application infrastructure. The following are a few benefits of using AuraJS ; they may help you choose this framework for your application: AuraJS is framework-agnostic. Though it works great with Backbone.js, you can use it for your JavaScript module architecture even if you aren't using Backbone.js. It utilizes the module pattern, application-level and module-level communication using the facade (sandbox) and mediator patterns. It abstracts away the utility libraries that you use (such as templating and DOM manipulation) so you can swap alternatives anytime you want. Managing objects and module communication One of the most important ways to keep the application code maintainable is to reduce the tight coupling between modules and objects. If you are following the module pattern, you should never let one module communicate with another directly. Loose coupling adds a level of restriction in your code, and a change in one module will never enforce a change in the rest of the application. Moreover, it lets you re-use the same modules elsewhere. But how can we communicate if there is no direct relationship? The two important patterns we use in this case are the observer and mediator patterns. Using the observer/PubSub pattern The PubSub pattern is nothing but the event dispatcher. It works as a messaging channel between the object (publisher) that fires the event and another object (subscriber) that receives the notification. We mentioned earlier that we can have an application-level event aggregator as a property of the Application object. This event aggregator can work as the common channel via which the other modules can communicate, and that too without interacting directly. Even at the module-level, you may need a common event dispatcher only for that module; the views, models, and collections of that module can use it to communicate with each other. However, publishing too many events via a dispatcher sometimes makes it difficult to manage them and you must be careful enough to understand which events you should publish via a generic dispatcher and which ones you should fire on a certain component only. Anyhow, this pattern is one of the best tools to design a decoupled system, and you should always have one ready for use in your module-based application. Summary This article dealt with one of the most important topics of Backbone.js-based application development. At the framework level, learning Backbone is quite easy and developers get a complete grasp over it in a very short period of time. Resources for Article: Further resources on this subject: Building an app using Backbone.js [article] Testing Backbone.js Application [article] Understanding Backbone [article]

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article-image-article-prototyping-recipes

Packt

21 Jan 2014

16 min read

Prototyping Recipes

Packt

21 Jan 2014

16 min read

0
0
1180

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Prototyping Recipes

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