使用枢纽模型数据作为Laravel 4的雄辩中的另一个模型的关系 [英] Using pivot model data as a relationship to another model in Laravel 4's Eloquent

问题描述

我有一个关于多对多关系的数据透视表，其中包括另一个模型的第三个索引参数。我想要能够使用雄辩来访问这个模型。

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.

在我的应用程序中，我有一个用户谁可以拥有许多主题和许多学期。当用户具有主题时，它也需要属于给定的学期。我有一个用户，主题和学期表，以及 subject_user 表（其中 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).

当我检索到用户我也希望能够获得会话 主题已通过枢轴连接

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');
    }
}

我想要做的是遵循，并且可以使用会话模型。

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

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

这样的事情是可能的，还是需要扩展到口才？

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

推荐答案

有一种方法可以通过创建一个扩展 Illuminate\Database\Eloquent\Relations\枢。虽然这种方法还需要为拥有这个数据枢纽的两个模型添加一些代码，以便在需要时使用新的数据透视图。

There is a way to do this by creating a class that extends Illuminate\Database\Eloquent\Relations\Pivot. 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.

此链接讨论了自定义数据透视图的实现型号：
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 Illuminate\Database\Eloquent\Relations\Pivot;

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);
    }
}

现在，您将可以访问该枢纽的关系被定义。

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

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

注意：您不会直接与此课程进行互动。在这两个模型之间需要枢纽时，它将创建而不是默认枢轴。

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 Doc参考文献：使用数据透视表有一个关于定义自定义数据透视模型的简短说明。

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

这篇关于使用枢纽模型数据作为Laravel 4的雄辩中的另一个模型的关系的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！