laravel 如何在laravel 5中的多对多关系中急切加载？
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how to eager load in a Many to Many relationship in laravel 5?
提问by Chriz74
My user tableand item tableare related by a many to many relationship, the item tablehas some data in foreign tables, example color tableI have a pivot table that relates the two.
My question is, if I want to retrieve all the items associated to a user with a color how do I get them with eager loading?
Myuser table和item table通过多对多关系相关，item table在外部表中有一些数据，例如color table我有一个将两者相关联的数据透视表。我的问题是，如果我想检索与具有颜色的用户关联的所有项目，我如何通过预先加载来获取它们？
I know that $user->itemwill retrieve all the items for that user.
我知道这$user->item将检索该用户的所有项目。
But if I want to eager load all the items for that user with the color attributes in one query, how do I do it? At the moment I am looping through the items associated to the user and lazy loading every data I need, for example
但是，如果我想在一个查询中使用颜色属性急切加载该用户的所有项目，我该怎么做？目前我正在遍历与用户关联的项目并延迟加载我需要的每个数据，例如
foreach($user->item as $i){
echo($i->item->color)
}
This means every cycle makes a new query...
这意味着每个周期都会产生一个新的查询......
here the models:
这里的模型：
User model:
用户模型：
public function item(){
return $this->belongsToMany('App\item')->withTimestamps();
}
item model:
物品型号：
public function user(){
return $this->belongsToMany('App\User');
}
and this the schema for the pivot table
这是数据透视表的架构
Schema::create('item_user', function(Blueprint $table) {
$table->unsignedInteger('user_id')->unsigned()->index();
$table->foreign('user_id')
->references('id')
->on('users')
->onDelete('cascade');
$table->unsignedInteger('item_id')->unsigned()->index();
$table->foreign('item_id')
->references('id')
->on('items')
->onDelete('cascade');
$table->timestamps();
});
回答by Luceos
You can simply use a Nested Eager Loading
您可以简单地使用嵌套的急切加载
Eager loading is done using with(): in your instance you could use the following:
急切加载是使用with(): 在您的实例中完成的，您可以使用以下内容：
public function item(){
return $this->belongsToMany('App\item')->withTimestamps()->with('color');
}
This will eager load the color on the "item". However you can also eager load immediately on the User model in your controller:
这将急切加载“项目”上的颜色。但是，您也可以立即在控制器中的 User 模型上立即加载：
User::with('items.color')->find(1);
I'm not sure based on your code that the relations/model is like this, but you get the point I guess.
根据你的代码，我不确定关系/模型是这样的，但我猜你明白了。
