問題描述

我有一個用于多對多關系的數據透視表，其中包括另一個模型的第三個索引參數.我希望能夠使用 Eloquent 訪問此模型.

I have a pivot table for a many to many relationship which includes a third index parameter for another model. I would like to be able to use Eloquent to access this model.

在我的應用程序中，我有一個 User，他可以擁有許多 Subjects 和許多 Semesters.當用戶擁有 Subject 時，它也需要屬于給定的 Semester.我有一個 users、subjects 和 semesters 表，以及一個 subject_user 表(其中有 user_id、subject_id 和 semester_id).

In my application, I have a User who can have many Subjects and many Semesters. When a user has a Subject, it needs to belong to a given Semester as well. I have a users, subjects and semesters table, as well as a subject_user table (which has user_id, subject_id and semester_id).

當我檢索 User 的主題時，我還希望能夠獲得 Subject 已連接到的 Session通過數據透視表.

When I retrieve the User's subjects, I would also like to be able to get the Session the Subject has been connected to through the pivot table.

class User
{
    public function subjects()
    {
        $this->belongsToMany('Subject')->withPivot('session_id');
    }
}

我希望能夠做的如下，并讓我可以使用 Session 模型.

What I would like to be able to do is as follows, and have the Session model available to me.

$user->subjects()->pivot->semester;

這樣的事情是可能的，還是需要對 Eloquent 進行擴展?

Is such a thing possible, or will this require an extension to Eloquent?

推薦答案

有一種方法可以通過創建一個擴展 IlluminateDatabaseEloquentRelationsPivot 的類來實現.盡管這種方法還需要向擁有此數據透視表的兩個模型添加一些代碼，以便它們在需要時使用新的數據透視表.

There is a way to do this by creating a class that extends IlluminateDatabaseEloquentRelationsPivot. Though this approach also requires adding some code to the two models that own this pivot so that they use the new Pivot when needed.

此鏈接討論自定義樞軸模型的實現:https://github.com/laravel/framework/issues/2093#issuecomment-39154456

This link discusses the implementation of the Custom Pivot Model: https://github.com/laravel/framework/issues/2093#issuecomment-39154456

use IlluminateDatabaseEloquentRelationsPivot;

class SubjectUser extends Pivot {
   // add your relationships back to User and Subject
    public function session() {
         // your relation to session here
    }
}

class Subject extends Eloquent {
    ...
    public function newPivot(Eloquent $parent, array $attributes, $table, $exists) {
        if ($parent instanceof User) {
            return new SubjectUser($parent, $attributes, $table, $exists);
        }
        return parent::newPivot($parent, $attributes, $table, $exists);
    }
}

class User extends Eloquent {
    ...
    public function newPivot(Eloquent $parent, array $attributes, $table, $exists) {
        if ($parent instanceof Subject) {
            return new SubjectUser($parent, $attributes, $table, $exists);
        }
        return parent::newPivot($parent, $attributes, $table, $exists);
    }
}

現在您將可以訪問已定義的樞軸關系.

Now you will have access to that pivot's relationship that have been defined.

$user->subjects->first()->pivot->session->...

注意:您不會直接與該課程互動.當這兩個模型之間需要樞軸時，會創建它而不是默認的樞軸.

Note: You will not be interacting with this class directly. It is created instead of the default Pivot when the pivot is needed between those 2 models.

Laravel 文檔參考:使用數據透視表 有一小段關于定義自定義樞軸模型.

Laravel Doc Reference: Working with Pivot Tables has a short passage about Defining a Custom Pivot Model.

這篇關于在 Laravel 4 的 Eloquent 中使用樞軸模型數據作為與另一個模型的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！