Model::bindModel and Model::unbindModel are powerful tools that allow you to adjust associations on the fly. However, they are often misused, taking the association definition out of the Model and placing it in the Controller. Changing the requirements of a bind done in this way means going through your controllers and changing the bindModel call, often in multiple places. Using unbindModel in a controller also means every time a new association is added you may need to go back into your controllers and unbind the new associations in order to optimize your code.

Here I show you how to add a simple method to your Model classes that allows your controllers to specify binds directly, in a cleaner, more proper way.

Place the following code in app/app_model.php

Model Class:

<?php 
class AppModel extends Model {
...
    var $assocs = array();
...
    function expects($array) {
        foreach ($array as $assoc) {
            $this->bindModel(
                array($this->assocs[$assoc]['type'] =>
                    array($assoc => $this->assocs[$assoc])));
        }
    }
...
}
?>
Now, in your Models, define the associations in an array called $assocs. The only difference between this definition and the standard association definitions is the inclusion of a new key: 'type', which should be 'hasOne', 'hasMany', 'belongsTo' or 'hasAndBelongsToMany'.

Model Class:

<?php 
class Title extends AppModel {

    var $assocs = array(
        'Book' => array(
            'type' => 'belongsTo',
            'className' => 'Book',
            'foreignKey' => 'collection_id',
        ),
        'Story' => array(
            'type' => 'hasOne',
            'className' => 'Story',
        ),
        'Album' => array(
            'type' => 'belongsTo',
            'className' => 'Album',
            'foreignKey' => 'collection_id',
        ),
        'Photo' => array(
            'type' => 'hasOne',
            'className' => 'Photo',
        ),
        'Post' => array(
            'type' => 'hasMany',
            'className' => 'Post',
            'order' => 'Post.id DESC',
        ),
    );
}
?>
Now, whenever you need to extend your results through an association, you can make a call to Model::expects() with the necessary values right before the query, and get the results you need.

Controller Class:

<?php 
TitlesController extends AppController {
    function list($id) {
        // establish necessary associations
        $this->Title->expects(array('Story', 'Post'));
        $this->Title->Post->expects(array('User'));
        $this->Title->recursive = 2;
        $results = $this->Title->read(null, $id);
    }
}
?>
That's it.

I still use the standard means of associations in most cases. For example, I will probably never need to show my Post without the User info, so my Post model has a $belongsTo = array('User') in its class definition. The above example of $this->Title->Post->expects(array('User')); would never be needed and was just included here to show you how the associations can work through recursion.

And now, with the way Models are loaded with CakePHP_1.1.11, this has an even greater affect. Models are only loaded when needed by a particular action.