問題描述

我有一個具有多個定義關系的復雜模型.在這個例子中，我想計算 Like 模型并創建一個名為 likes 的屬性，以便它可以從 REST 服務返回.

I have a complex Model with multiple defined relations. In this example I would want to count the Like model and create a property named likes so it can be returned from a REST service.

是否可以將模型計數預先加載到動態屬性中?

Is it possible to eager load a model count into a dynamic property?

$beat = Post::with(
         array(
            'user',
            'likes' => function($q){
                $q->count();
            }
        ))
        ->where('id', $id)
        ->first();

推薦答案

假設您有 Post->hasMany->Like 關系，并且您已聲明 Likes 關系為:

Assuming you are having Post->hasMany->Like relationship and you have declared likes relationship as:

class Post{

  public function likes(){
   return $this->hasMany('Like');
  }
}

創建一個新函數，比如 likeCountRelation 為:

create a new function say likeCountRelation as:

public function likeCountRelation()
{
    $a = $this->likes();

    return $a->selectRaw($a->getForeignKey() . ', count(*) as count')->groupBy($a->getForeignKey());
}

現在您可以將 __get() 函數重寫為:

now you can override __get() function as:

public function __get($attribute)
{

    if (array_key_exists($attribute, $this->attributes)) {
        return $this->attributes[$attribute];
    }

    switch ($attribute) {

        case 'likesCount':
            return $this->attributes[$attribute] = $this->likesCountRelation->first() ? $this->likesCountRelation->first()->count : 0;
            break;

        default:
            return parent::__get($attribute);

    }
}

或者你可以使用 getattribute 函數:

or you can use getattribute function as :

public function getLikesCountAttribute(){
 return $this->likesCountRelation->first() ? $this->likesCountRelation->first()->count : 0;
}

并且只需將 likesCount 作為 $post->likesCount 訪問，您甚至可以像這樣急切加載它:

and simply access likesCount as $post->likesCount you can even eager load it like:

$posts=Post::with('likesCountRelation')->get();
 foreach($post as $post){
  $post->likesCount;
 }

注意:相同的邏輯可用于變形許多關系.

NOTE: Same logic can be used for morph many relationships.

這篇關于laravel 4 雄辯的急切加載關系計數的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！