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Has Many - 關聯 - Orm 套件

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2023-12-01

Orm 是 物件关联对映(Object Relational Mapper) 的简写,它做两件事:
对应你资料库里的资料列到物件, 并能让你在这些物件之间建立关係。
它紧随 活动记录模式( Active Record Pattern),但也受到其他系统的影响。

关联:Has Many

Specifies a one-to-many relationship to another model. The target model must include a "Belongs To" reference to the current model to allow the inverse relationship.

範例

Let's say we have a model Model_Post and it has many Model_Comments (which in turn belong to the post). The ID of the Model_Post is saved with the Model_Comment instance in its own table. This means the comments table will have a column post_id (or something else you configure), while the posts table won't mention the comments. If you keep to the defaults all you need to do is add 'comments' to the $_has_many static property of the Model_User:

protected static $_has_many = array('comments');

Below are examples for establishing and breaking has-many relations:

// 主要及关联物件两者都是新的:
$post = new Model_Post();
$post->comments[] = new Model_Comment();
$post->save();

// both main and related object already exist
$post = Model_Post::find(1);
$post->comments[6] = Model_Comment::find(6); // assigning it to comments[6] is not required but recommended
$post->save();

// break the relationship established above
$post = Model_Post::find(1);
unset($post->comments[6]);
$post->save();

Full config example with defaults as values

// 在有多个 comments 的 Model_Post 中
protected static $_has_many = array(
	'comments' => array(
		'key_from' => 'id',
		'model_to' => 'Model_Comment',
		'key_to' => 'post_id',
		'cascade_save' => true,
		'cascade_delete' => false,
	)
);