Swift Cookbook

To download Xcode from the App Store, just open App Store from your dock or your applications folder.

The first time you open the App Store, it will ask you for your Apple ID details (email and password). After opening this application, just search for xcode in the textbox, which is located on the upper-right corner of this application.

Make sure that you are installing Xcode from the right vendor (Apple); sometimes, we get results that lead us to think that they are what we want but they aren't.

Once you have found the Xcode app, just click on the Install button, and the next step is to go for coffee, or you can call a friend, because Xcode is 2.2 gigas, which means that it will take a while to download, so take a break now.

To check if Xcode has finished the installation, you just need to open the Applications folder or the Launchpad app, then have a look to see whether there is any progress bar under the Xcode icon.

The first step is to open your web browser; go to http://developer.apple.com, log in where it says Member Center. If you are a member of more than one team, it will ask you which account you want to use. Choose the most appropriate one.

After this, you will see a table with some options, choose iOS Dev Center or Mac Dev Center.

After downloading the DMG file, double-click on it and drag the Xcode icon into your Application folder. Remember that you need the administrator's permission to copy files into the Applications folder.

You can also install Xcode onto a different path like your home directory, but I wouldn't recommend this if it's not necessary.

Now, Xcode is asking you about the project you want to start or open. Check the option that says Create a new Xcode project.

If, for any reason, this window is not shown to you, there is always the option to go to File (on the menu bar) | New | Project.

The next step is to choose the type of project that you want to develop. To do this example, I will use a Single View Application for iOS, but I'll make comments if there is anything different on OS X applications, or for another type of project.

The next dialog will ask you for some project information, one example being the programming language that you want to use. In this example, we will use Swift.

Choose Swift as language and it will create the application with its delegate, with Swift code. Make sure that Core Data is unchecked to prevent having its code on the app delegate.

You will also notice that Swift iOS applications now have no files called main.m, main.mm, or main.swift. OS X apps have a main.swift file, but it is smaller than the previous main.m file.

As you should already know, the product name is your application name, the organization name is the proprietary of this software, and the organization identifier is the reversed Internet domain, for example, uk.co.packtpub instead of packtpub.co.uk.

Note that now there is no checkbox for creating unit tests because by default, it is created for you using XCTest. If you don't want it, just remove the group from your project. I wouldn't remove it, it usually doesn't hurt.

Now, it's time to choose a folder to store our project. Remember that during the development, you can add files, which will be stored in different locations. I don't recommend this kind of practice, but if you have to do so, try to have your project close to these files.

I also recommend you to check the option to use a Git repository, except if you have a subversion repository, of course. Even if you are the only developer, it's important to have a version control system. Remember that we are humans, and sometimes, we make mistakes and so have to go back.

Once you have the project created, press the play button to see it working. If it's the first time you have installed Xcode, it will show you a dialog asking you to enable the developer mode. Click on the Enable button if you have the administrator password.

Ok, now you have your project up and running.

Once you've created a project, click on the navigator project icon or press command + 1 if you prefer a keyboard shortcut, then click on your project icon (the first icon). Now, click on Build Settings.

Look for Embedded content contains swift code; In this case, we will select NO, but of course, if you know that there is any extra content created with Swift, you should select YES.

Go to the General tab and scroll down; you can see where you can add the embedded binaries.

Now, look for Optimization Level. Here is where you tell the compiler how much time it should expend trying to make your code faster or compressing it. Usually, when we are developing (debug mode), we set for no optimization (-O0); however, when we are going to create the final product (release mode), we will usually set an optimization level such as-Os, which means fastest and smallest.

Another important option is Import paths. This tells Swift where it should look for Swift modules. If you are linking your project with external libraries, you may need to specify where the module.map file is. If you have more than one path to search, you need to set them one per line. If you have different paths for debug and release, you can still use variables such as $(CONFIGURATION) or $(TARGET).

After creating a new project, let's create a new file by navigating to File | New | File.... Now, choose Swift File and name it CustomLog.swift.

Now, add the following code:

func printLog(message: NSString){
    #if VERBOSE_LOG
        #if os(OSX)
            let OS="OS X"
        #else
            let OS="iOS"
        #endif
        
        #if arch(arm) || arch(arm64)
            let devicetype = "Mobile device"
        #elseif arch(x86_64) || arch(i386)
            let devicetype = "Computer"
        #else
            let devicetype = "Unkown"
        #endif
        
        NSLog("%@ on a %@ - %@", OS, devicetype, message)
    #endif
}

Now, go to the viewDidLoad method of your view controller, and add a call for this function, like this:

printLog("Hello World")

Try pressing play now; what do you see? The answer is—nothing! The reason is that the compiler knows nothing about the macro VERBOSE_LOG, which means that this macro is interpreted as false and the only thing that is created is an empty function.

Now, go back to your project build settings, search for other swift flags, and add -DVERBOSE_LOG, as shown in the following screenshot:

Click on play again and you will see the log message.

Once you've opened the project, click on the project navigator, then click on the combobox that shows our project, and select the target Chapter 1 if it's not selected yet.

Now, have a look at the option called Team. In the case of programming a Mac application, this combobox is enabled only if you select the signing option to Mac App Store or Developer ID.

Usually, the team option starts with None selected. Click over this combobox and select Add Account.

After selecting to add an account, Xcode will ask for your Apple Developer Program login data (e-mail and password). If you don't have it, you have the option to join the program.

Once you've added this, you are supposed to use your account and run your app. If you have a device attached to your Mac, you can go to the Window option on the menu bar, and then you can select the Devices option.

Your device should appear on the dialog, Xcode could take a while to read the device's symbols. In case of having this device attached for the first time, you will see that you will have to ask to change the status of this device to developer mode.

When you get the green light, it means that your device is ready to be used for development; now, go back to your project and change from the simulator to your device.

If the device is enabled, but not listed by Xcode, it could mean that you have to decrease the iOS Deployment Target, which can be found on the project setting, under the Info tab.

Just type xcode-select -p; this should give to you one path, for example, /Applications/Xcode.app/Contents/Developer, If you don't have more Xcode versions installed in your machine, you shouldn't worry about the path, it will probably be right. If for any reason you have more than one Xcode installed on your machine, you will need to change it by typing xcode-select -s /Applications/XCODE VERSION.app/Contents/Developer.

Now, go to your project directory and type xcodebuild -target "Chapter 1" -configuration Debug. After this, you will see lots of commands on screen, but the most important message is the last one that should be ** BUILD SUCCEEDED **; which means that the project was built without errors.

The first step is to find where the Swift command is; even if you have used the xcode-select command, it is possible that the Swift command is not accessible from your PATH variable. So, you can localize your Swift command using find /Applications/Xcode.app -name swift -a -type f. In my case, I got /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift. However, current versions of Xcode have the Swift command at /usr/bin. If it is necessary, add this directory to your PATH variable with the command export PATH="$PATH:/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/". At this moment, we can enter into the Swift interpreter just typing swift.

If you want to use Swift from the command line, sometimes, it's a good idea to have this PATH variable set permanently. To make this, we need to add the previous command into our .profile file, such as echo 'export PATH="$PATH:/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/" ' >> $HOME/.profile && chmod +x $HOME/.profile. From now on, if you restart your computer, it won't be necessary to look for the Swift path and set the PATH environment variable again.

Now, let's enter into our Swift command line and type the following code:

var dividend = [3,2,1,0]
var divisor = 6

You will see a message showing the content of these variables after typing each of them. Now, type the following loop code:

for i in dividend { 
      println("\(divisor) / \(i) = \(divisor / i)")  
}

Now, you can see that we will receive the following result:

6 / 3 = 2
6 / 2 = 3
6 / 1 = 6
Execution interrupted. Enter Swift code to recover and continue.
Enter LLDB commands to investigate (type :help for assistance.)

As you can see, the last option failed because we can't divide by 0 and that's a fast way we can test some code, using the command line. Most of the time, we will test using a playground, but sometimes using the command line is much faster.

Open a Finder window again and use the shortcut command + Shift + U, or open the utilities folder from your Launchpad. Now, open the terminal and go to your project folder.

Change your folder using the terminal by typing cd followed by a white space. Now, without closing your terminal, open the Finder window, then go to your project folder, drag the folder from the title bar to your terminal window, and then press the Enter key.

Now, just type the following commands:

git init
git add .
git commit -m "Initial commit"

Now, you can open your project and notice that Xcode already recognizes the VCS. If you want to be sure of it, modify a file, save it with command + S and check that you have the letter M on the right side of your file on the project navigator.

Once you are happy with your changes, you can deliver them by right-clicking on AppDelegate.swift, then go to the Source Control option and select Commit AppDelegate.swift.

Then, a dialog asking for a description will appear, write about your modification as comment, and click on commit 1 file.