Chapter 4. Models and Collections

Like most modern frameworks and platforms, these days Magento embraces an Object Relational Mapping (ORM) approach over raw SQL queries. Though the underlying mechanism still comes down to SQL, we are now dealing strictly with objects. This makes our application code more readable, manageable, and isolated from vendor-specific SQL differences. Model, resource, and collection are three types of classes working together to allow us full entity data management, from loading, saving, deleting, and listing entities. The majority of our data access and management will be done via PHP classes called Magento models. Models themselves don't contain any code for communicating with the database.

The database communication part is decoupled into its own PHP class called resource class. Each model is then assigned a resource class. Calling load, save, or delete methods on models get delegated to resource classes, as they are the ones to actually read, write, and delete data from the database. Theoretically, with enough knowledge, it is possible to write new resource classes for various database vendors.

Next to the model and resource classes, we have collection classes. We can think of a collection as an array of individual model instances. On a base level, collections extend from the \Magento\Framework\Data\Collection class, which implements \IteratorAggregate and \Countable from Standard PHP Library (SPL) and a few other Magento-specific classes.

More often than not, we look at model and resource as a single unified thing, thus simply calling it a model. Magento deals with two types of models, which we might categorize as simple and EAV models.

In this chapter, we will cover the following topics:

• Creating a miniature module
• Creating a simple model
• The EAV model
• Understanding the flow of schema and data scripts
• Creating an install schema script (InstallSchema.php)
• Creating an upgrade schema script (UpgradeSchema.php)
• Creating an install data script (InstallData.php)
• Creating an upgrade data script (UpgradeData.php)
• Entity CRUD actions
• Managing collections