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Models

Models are the classes that form the business layer in your application. They should be responsible for managing almost everything regarding your data, its validity, and its interactions, as well as the evolution of the information workflow in your domain.

Usually, model classes represent data and are used in CakePHP applications for data access. They generally represent a database table but can be used to access anything that manipulates data such as files, external web services, or iCal events.

A model can be associated with other models. For example, a Recipe may be associated with an Author as well as an Ingredient.

This section will explain what features of the model can be automated, how to override those features, and what methods and properties a model can have. It will explain the different ways to build associations for your data. It will describe how to find, save, and delete data. Finally, it will look at Datasources.

Understanding Models

A Model represents your data model. In object-oriented programming, a data model is an object that represents a thing such as a car, a person, or a house. A blog, for example, may have many blog posts and each blog post may have many comments. The Blog, Post, and Comment are all examples of models, each associated with another.

Here is a simple example of a model definition in CakePHP:

App::uses('AppModel', 'Model');
class Ingredient extends AppModel {
    public $name = 'Ingredient';
}

With just this simple declaration, the Ingredient model is endowed with all the functionality you need to create queries and to save and delete data. These methods come from CakePHP’s Model class by the magic of inheritance. The Ingredient model extends the application model, AppModel, which in turn extends CakePHP’s internal Model class. It is this core Model class that bestows the functionality onto your Ingredient model. App::uses('AppModel', 'Model') ensures that the model is loaded when it is needed.

The intermediate class, AppModel, is empty. If you haven’t created your own, it is taken from the CakePHP core folder. Overriding the AppModel allows you to define functionality that should be made available to all models within your application. To do so, you need to create your own AppModel.php file that resides in the Model folder, as do all other models in your application. Creating a project using Bake will automatically generate this file for you.

See also Behaviors for more information on how to apply similar logic to multiple models.

Back to our Ingredient model. In order to work on it, create the PHP file in the /app/Model/ directory. By convention, it should have the same name as the class, which for this example will be Ingredient.php.

Note

CakePHP will dynamically create a model object for you if it cannot find a corresponding file in /app/Model. This also means that if your model file isn’t named correctly (for instance, if it is named ingredient.php or Ingredients.php rather than Ingredient.php), CakePHP will use an instance of AppModel rather than your model file (which CakePHP assumes is missing). If you’re trying to use a method you’ve defined in your model, or a behavior attached to your model, and you’re getting SQL errors that are the name of the method you’re calling, it’s a sure sign that CakePHP can’t find your model and you need to check the file names, your application cache, or both.

Note

Some class names are not usable for model names. For instance, “File” cannot be used, since “File” is a class that already exists in the CakePHP core.

When your model is defined, it can be accessed from within your Controller. CakePHP will automatically make the model available for access when its name matches that of the controller. For example, a controller named IngredientsController will automatically initialize the Ingredient model and attach it to the controller at $this->Ingredient:

class IngredientsController extends AppController {
    public function index() {
        //grab all ingredients and pass it to the view:
        $ingredients = $this->Ingredient->find('all');
        $this->set('ingredients', $ingredients);
    }
}

Associated models are available through the main model. In the following example, Recipe has an association with the Ingredient model:

class Recipe extends AppModel {

    public function steakRecipes() {
        $ingredient = $this->Ingredient->findByName('Steak');
        return $this->findAllByMainIngredient($ingredient['Ingredient']['id']);
    }
}

This shows how to use models that are already linked. To understand how associations are defined, take a look at the Associations section