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Containable

A new addition to the CakePHP 1.2 core is the ContainableBehavior. This model behavior allows you to filter and limit model find operations. Using Containable will help you cut down on needless wear and tear on your database, increasing the speed and overall performance of your application. The class will also help you search and filter your data for your users in a clean and consistent way.

Containable allows you to streamline and simplify operations on your model bindings. It works by temporarily or permanently altering the associations of your models. It does this by using the supplied containments to generate a series of bindModel and unbindModel calls.

To use the new behavior, you can add it to the $actsAs property of your model:

class Post extends AppModel {
    var $actsAs = array('Containable');
}

You can also attach the behavior on the fly:

$this->Post->Behaviors->attach('Containable');

Usando o Containable

Para ver como o Containable funciona, vamos ver alguns exemplos. Primeiramente vamos começar com uma chamada find() em um model chamado Post. Digamos que nosso Post possa ter vários comentários (Post hasMany Comment) e que possa ter e pertence a muitas tgs (Post hasAndBelongsToMany Tag). A quantidade de dados recuperados em uma chamada find() normal poderá ser bem extensa:

debug($this->Post->find('all'));

[0] => Array
        (
            [Post] => Array
                (
                    [id] => 1
                    [title] => Primeiro post
                    [content] => aaa
                    [created] => 2008-05-18 00:00:00
                )
            [Comment] => Array
                (
                    [0] => Array
                        (
                            [id] => 1
                            [post_id] => 1
                            [author] => Daniel
                            [email] => dan@example.com
                            [website] => http://example.com
                            [comment] => Primeiro comentário
                            [created] => 2008-05-18 00:00:00
                        )
                    [1] => Array
                        (
                            [id] => 2
                            [post_id] => 1
                            [author] => Sam
                            [email] => sam@example.net
                            [website] => http://example.net
                            [comment] => Segundo comentário
                            [created] => 2008-05-18 00:00:00
                        )
                )
            [Tag] => Array
                (
                    [0] => Array
                        (
                            [id] => 1
                            [name] => Incrível
                        )
                    [1] => Array
                        (
                            [id] => 2
                            [name] => Fermento
                        )
                )
        )
[1] => Array
        (
            [Post] => Array
                (...

Para algumas telas de sua aplicação, você pode não precisar de tanta informação a partir do model Post. Uma das coisas que o ContainableBehavior faz é ajudar você a enxugar o retorno de uma chamada find().

Por exemplo, para obter apenas as informações referentes ao Post em si, você pode fazer o seguinte:

$this->Post->contain();
$this->Post->find('all');

Você também pode invocar a mágica do Containable de dentro de uma chamada ao find():

$this->Post->find('all', array('contain' => false));

Feito isto, você obtem um resultado bem mais conciso:

[0] => Array
        (
            [Post] => Array
                (
                    [id] => 1
                    [title] => Primeiro post
                    [content] => aaa
                    [created] => 2008-05-18 00:00:00
                )
        )
[1] => Array
        (
            [Post] => Array
                (
                    [id] => 2
                    [title] => Segundo post
                    [content] => bbb
                    [created] => 2008-05-19 00:00:00
                )
        )

Este tipo de ajuda não é algo novo: na verdade, você já poderia fazer isso mesmo sem o ContainableBehavior com algo assim:

$this->Post->recursive = -1;
$this->Post->find('all');

O Containable realmente vai mostrar sua importância quando você tiver associações compleas e quiser filtrar as coisas que estiverem num mesmo nível. A propriedade $recursive do model é útil se você quiser remover um nível completo de recursão, mas não vai adiantar se você quser selecionar e escolhar o que manter em cada nível. Vejamos como as coisas funcionam ao se usar o método contain().

O primeiro argumento do métod contain aceita o nome ou um array de nomes do models que queremos manter na operação de busca. Se quisermos recuperar todos os posts e suas respectivas tags (sem as informações de comentários), poderíamos fazer algo como:

$this->Post->contain('Tag');
$this->Post->find('all');

Novamente, podemos também usar o índice contain dentro de uma chamada find():

$this->Post->find('all', array('contain' => 'Tag'));

Sem o Containable, você acabaria precisaria usar o método unbindModel() do model várias vezes para remover diversos models do resultado. O Containable cria uma maneira simples e clara de se obter o mesmo resultado.

Containing deeper associations

Containable also goes a step deeper: you can filter the data of the associated models. If you look at the results of the original find() call, notice the author field in the Comment model. If you are interested in the posts and the names of the comment authors — and nothing else — you could do something like the following:

$this->Post->contain('Comment.author');
$this->Post->find('all');

//or..

$this->Post->find('all', array('contain' => 'Comment.author'));

Here, we’ve told Containable to give us our post information, and just the author field of the associated Comment model. The output of the find call might look something like this:

[0] => Array
        (
            [Post] => Array
                (
                    [id] => 1
                    [title] => First article
                    [content] => aaa
                    [created] => 2008-05-18 00:00:00
                )
            [Comment] => Array
                (
                    [0] => Array
                        (
                            [author] => Daniel
                            [post_id] => 1
                        )
                    [1] => Array
                        (
                            [author] => Sam
                            [post_id] => 1
                        )
                )
        )
[1] => Array
        (...

As you can see, the Comment arrays only contain the author field (plus the post_id which is needed by CakePHP to map the results).

You can also filter the associated Comment data by specifying a condition:

$this->Post->contain('Comment.author = "Daniel"');
$this->Post->find('all');

//or...

$this->Post->find('all', array('contain' => 'Comment.author = "Daniel"'));

This gives us a result that gives us posts with comments authored by Daniel:

[0] => Array
        (
            [Post] => Array
                (
                    [id] => 1
                    [title] => First article
                    [content] => aaa
                    [created] => 2008-05-18 00:00:00
                )
            [Comment] => Array
                (
                    [0] => Array
                        (
                            [id] => 1
                            [post_id] => 1
                            [author] => Daniel
                            [email] => dan@example.com
                            [website] => http://example.com
                            [comment] => First comment
                            [created] => 2008-05-18 00:00:00
                        )
                )
        )

Additional filtering can be performed by supplying the standard Model->find() options:

$this->Post->find('all', array('contain' => array(
    'Comment' => array(
        'conditions' => array('Comment.author =' => "Daniel"),
        'order' => 'Comment.created DESC'
    )
)));

Here’s an example of using the ContainableBehavior when you’ve got deep and complex model relationships.

Let’s consider the following model associations:

User->Profile
User->Account->AccountSummary
User->Post->PostAttachment->PostAttachmentHistory->HistoryNotes
User->Post->Tag

This is how we retrieve the above associations with Containable:

$this->User->find('all', array(
    'contain'=>array(
        'Profile',
        'Account' => array(
            'AccountSummary'
        ),
        'Post' => array(
            'PostAttachment' => array(
                'fields' => array('id', 'name'),
                'PostAttachmentHistory' => array(
                    'HistoryNotes' => array(
                        'fields' => array('id', 'note')
                    )
                )
            ),
            'Tag' => array(
                'conditions' => array('Tag.name LIKE' => '%happy%')
            )
        )
    )
));

Keep in mind that contain key is only used once in the main model, you don’t need to use “contain” again for related models

When using “fields” and “contain” options - be careful to include all foreign keys that your query directly or indirectly requires. Please also note that because Containable must be attached to all models used in containment, you may consider attaching it to your AppModel.

Using Containable with pagination

Here’s an example of how to contain associations when paginating.

$this->paginate['User'] = array(
    'contain' => array('Profile', 'Account'),
    'order' => 'User.username'
);

$users = $this->paginate('User');

By including the “contain” parameter in the $paginate property it will apply to both the find(“count”) and the find(“all”) done on the model

ContainableBehavior options

The ContainableBehavior has a number of options that can be set when the Behavior is attached to a model. The settings allow you to fine tune the behavior of Containable and work with other behaviors more easily.

  • recursive (boolean, optional) set to true to allow containable to automatically determine the recursiveness level needed to fetch specified models, and set the model recursiveness to this level. setting it to false disables this feature. The default value is true.

  • notices (boolean, optional) issues E_NOTICES for bindings referenced in a containable call that are not valid. The default value is true.

  • autoFields: (boolean, optional) auto-add needed fields to fetch requested bindings. The default value is true.

You can change ContainableBehavior settings at run time by reattaching the behavior as seen in Using behaviors

ContainableBehavior can sometimes cause issues with other behaviors or queries that use aggregate functions and/or GROUP BY statements. If you get invalid SQL errors due to mixing of aggregate and non-aggregate fields, try disabling the autoFields setting.

$this->Post->Behaviors->attach('Containable', array('autoFields' => false));