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Magento PHP Developer????s Guide, 2nd Edition
Magento PHP Developer????s Guide, 2nd Edition

Magento PHP Developer????s Guide, 2nd Edition: Get up and running with the highly customizable and powerful e-commerce solution, Magento

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Magento PHP Developer????s Guide, 2nd Edition

Chapter 2. ORM and Data Collections

Collections and models are the bread and butter of everyday Magento development. In this chapter, we will introduce the reader to the Magento ORM system, and we will learn how to work with data collections and the EAV system properly. As most modern systems, Magento implements an object-relational mapping (ORM) system.

Object-relational mapping (ORM, O/RM, and O/R mapping) in computer software is a programming technique for converting data between incompatible type systems in object-oriented programming languages. This creates, in effect, a "virtual object database" that can be used from within the programming language.

In this chapter, we will cover the following topics:

  • Magento Models
  • Anatomy of a Magento Data Model
  • EAV and EAV models
  • Working with Direct SQL queries

We will also be working with several snippets of code to provide an easy framework to experiment and play around with Magento.

Note

The interactive examples in this chapter...

Magento Model anatomy

As we learned in the previous chapter, Magento data models are used to manipulate and access the data. The model layer is divided into two fundamental types, simple models and EAV:

  • Simple models: These model implementations are a simple mapping of one object to one table, meaning our object attributes match each field and our table structure.
  • Entity Attribute Value models: This type of models, known as EAV models, are used to describe entities with a dynamic number of attributes.

Note

It is important to clarify that not all Magento models extend or make use of the ORM. Observers are a clear example of simpler model classes that are not mapped to a specific database table or entity.

In addition to that, each Model type is formed by the following layers:

  • Model class: This is where most of our business logic resides. Models are used to manipulate the data, but they don't access it directly.
  • Resource Model class: Resource Models are used to interact with the database on...

The EAV model

EAV stands for entity, attribute, and value and is probably the most difficult concept for new Magento developers to grasp. While the EAV concept is not unique to Magento, it is rarely implemented on modern systems. Additionally, a Magento implementation is not a simple one.

The EAV model

What is EAV?

In order to understand what EAV is and what its role within Magento is, we need to break down parts of the EAV model:

  • Entity: This represents the data items (objects) inside Magento products, customers, categories, and orders. Each entity is stored in the database with a unique ID.
  • Attribute: These are our object properties. Instead of having one column per attribute on the product table, attributes are stored on separate sets of tables.
  • Value: As the name implies, it is simply the value link to a particular attribute.

This data model is the secret behind Magento's flexibility and power, allowing entities to add and remove new properties without having to make any changes to the code, templates...

Working with Magento collections

If you look back at the previous code example, you will notice that I'm not only instantiating a product model, but I'm also calling the getCollection() method. The getCollection() method is part of the Mage_Core_Model_Abstract class, meaning, every single model inside Magento can call this method.

Tip

All collections inherit from Varien_Data_Collection.

A Magento collection is basically a model that contains other models. So instead of using an array to hold a collection of products, we will use a product collection. Collections not only provide a convenient data structure to group models, they also provide special methods that we can use to manipulate and work with a collection of entities.

Some of the most useful collection methods are:

  • addAttributeToSelect: To add an attribute to the entities in a collection; * can be used as a wildcard to add all the available attributes
  • addFieldToFilter: To add an attribute filter to a collection; this function...

Using Direct SQL

So far we have learned how Magento data models and ORM systems provide a clean and simple way to access, store, and manipulate our data. Before we jump right into this section and learn about the Magento database adapters and how to run raw SQL queries, I feel it is important that we understand why you should avoid using what you are about to learn in this section as much as possible.

Magento is an extremely complex system, and as we've also learned in the previous chapter, a framework driven in part by events. Just saving a product will trigger half a dozen different events, each doing a different task. This will not happen if you decide to just create a query and update a product directly. So, as developers, we must be extremely careful and be sure there is a justifiable reason to go outside the ORM.

That said, there are of course scenarios when being able to work with the database directly comes in extremely handy and is actually simpler than working with the Magento...

Summary

In this chapter, we have learned about Magento models, their inheritance and purpose, and how Magento uses resources and collections to implement its own ORM.

We also learned about EAV models and how they are structured to provide Magento with data flexibility and extensibility that both merchants and developers can take advantage of.

Finally, we saw how developers can access the database directly by writing DirectSQL and using the Magento resource adapters.

The chapters so far have been more theory than practice. This has been done with the intention of guiding you through the complexity of Magento and providing you with the tools and knowledge that you require for the rest of the book. For the remaining chapters of the book, we will take a more hands-on approach and start building extensions, incrementally applying all the concepts we have learned so far.

Our next chapter is called Frontend Development where we will start getting our feet wet and develop our first Magento extension...

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Description

This book is written for PHP developers who are familiar with frameworks such as Zend or CakePHP and want to start developing and working with Magento. No prior knowledge of Magento is required.

Who is this book for?

This book is written for PHP developers who are familiar with frameworks such as Zend or CakePHP and want to start developing and working with Magento. No prior knowledge of Magento is required.
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Publication date : Jul 30, 2015
Length: 260 pages
Edition : 1st
Language : English
ISBN-13 : 9781783554195
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Table of Contents

10 Chapters
1. Magento Fundamentals for Developers Chevron down icon Chevron up icon
2. ORM and Data Collections Chevron down icon Chevron up icon
3. Frontend Development Chevron down icon Chevron up icon
4. Backend Development Chevron down icon Chevron up icon
5. The Magento API Chevron down icon Chevron up icon
6. Testing and Quality Assurance Chevron down icon Chevron up icon
7. Deployment and Distribution Chevron down icon Chevron up icon
A. Hello Magento Chevron down icon Chevron up icon
B. Understanding and Setting Up Our Development Environment Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Empty star icon Empty star icon Empty star icon 2
(4 Ratings)
5 star 25%
4 star 0%
3 star 0%
2 star 0%
1 star 75%
Janet Howarth Jan 06, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Xmas present for my brother he say brill
Amazon Verified review Amazon
Alex Dec 18, 2017
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
Die Beispiele aus dem Buch haben viele Fehler. Ich habe den Verlag kontaktiert und die haben mir den Code aus dem Edition 1 zur Verfügung gestellt. Für diesen Preis ist das echt unverschämt!
Amazon Verified review Amazon
Sin Mar 18, 2018
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
Very disappointing book. Full of so many typos that you'll need another reference just to make sense of the code. Missing letter, incorrect cases, nonsensical sentences, and syntax errors are just some of the mistakes that have been left in this book. If you can cope with this you'll still find the book incredibly lazy - many topics and code blocks simply aren't explained. Even as an experienced developer I got frustrated with the number of times functions/methods/classes were introduced with absolutely no explanation. Magento is a very complex platform and this book is so poorly written that it is utterly useless.If like me you've found yourself having to maintain an older Magento system, you're better off sifting through the official documentation. Whilst it's all over the place it's still better than this book.
Amazon Verified review Amazon
Warren R. Nov 01, 2015
Full star icon Empty star icon Empty star icon Empty star icon Empty star icon 1
This book has great potential, but is incomplete. This is especially brutal given its high price. In particular:- The code for this book only matches the first edition and is incomplete- Many URLs in the book do not work- I tried to contact the publisher before writing this, but they just sent me the first edition's code
Amazon Verified review Amazon
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