問題描述

假設我有一個像這樣的 Conversation 模型:

Suppose I have a Conversation model like this :

class Conversation extends Model
{
    public function questions (){
        return $this->hasMany('AppQuestion','conversation_id','conversation_id');
    }
    public function category ()
    {
        return $this->belongsTo('AppCategory', 'cat', 'cat_id');
    }

}

還有一個像這樣的 Question 模型:

And a Question model like this:

class Question extends Model
{
    public function conversation ()
    {
        return $this->belongsTo('AppConversation', 'conversation_id', 'conversation_id');
    }
}

如您所見，這兩者之間存在 hasMany 關系.

As you can see there is a hasMany relation between those two.

另一方面，有一個像下面這樣的 Category 與 Conversation 模型有關系:

In the other hand there is a Category like below that has a relation with Conversation model :

class Category extends Node
{
    public function conversations (){
        return $this->hasMany('AppConversation','cat','cat_id');
    }
}

現在我想將一個名為 question_count 的屬性附加到 Category 來計算每個類別的對話的所有問題.為此，我添加了這個:

Now I want to append an attribute named question_count to Category that counts all questions of conversations of each category. for that I added this :

    public function getQuestionsCountAttribute ()
    {
        return $this->conversations->questions->count();
    }

但是在獲取類別時出現此錯誤:

But when fetch a category I got this error :

ErrorException in Category.php line 59:
Undefined property: IlluminateDatabaseEloquentCollection::$questions

我做了什么?如何在最小服務器過載的情況下計算關系的關系?

What did I do? how can I count relations of a relation with minimum server overloading?

我使用的是 Laravel 5.3.4.

I am using laravel 5.3.4.

推薦答案

我認為這里你需要一個有很多的關系.

I think that you need a has many through relationship here.

你做錯了什么:

當你寫$this->conversations->questions時，這是行不通的，因為questions是單個對話的關系 而不是對話的集合(這里，$this->conversations 是一個集合)

When you write $this->conversations->questions, this can't work, because the questions are a relation of a single conversation and not of a collection of conversations (here, $this->conversations is a Collection)

解決辦法:

使用 hasManyThrough 關系:

Using hasManyThrough relation:

您可以在在此頁面上找到有關此關系的文檔，如果我的解釋不好

You can find the documentation for this relation on this page, if my explanation is bad

基礎是，你需要在你的 Category 模型上定義一個關系:

The basics are, you need to define a relation on your Category model:

class Category extends Node
{
    public function conversations ()
    {
        return $this->hasMany('AppConversation');
    }

    public function questions ()
    {
        return $this->hasManyThrough('AppQuestion', 'AppConversation');
    }
}

(我會讓你查看非標準外鍵的文檔)

(I will let your look into the documentation for your non standards foreign keys)

然后你應該可以使用:$category->questions->count()

這篇關于Laravel 中關系的計數關系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！