从用户到帖子和类别的多态多对多 [英] Polymorphic many to many from User to Post and Category

问题描述

我需要实现一个Twitter之类的关注系统，但除了一个用户之外，用户可以关注许多Post并且可以关注整个Category，或者用户可以关注User.

I need to implement a follow system like twitter but with exception a user can follow many Post and can follow whole Category or a user can follow a User.

我想出了这种关系.我正在使用Laravel 5.1

I have come up with this relationship. I am using Laravel 5.1

用户模型

public function followers()
{
   return $this->belongsToMany('App\User', 'user_follows', 'user_id', 'follow_id');
}

public function follows()
{
   return $this->belongsToMany('App\User', 'user_follows', 'follow_id', 'user_id');
}

并遵循类别

类别模型

public function followers()
{
   return $this->belongsToMany('App\User', 'category_follows', 'user_id', 'category_id');
}

和Post的用法相同，如您所见，我需要3个表(user_follows, category_follows, post_follows)才能完成这项工作.

and for Post is the same way, as you can see I need 3 tables (user_follows, category_follows, post_follows) to make this work.

我知道有Polymorphic Relation，但是我不能把头缠在它上面. 请帮助我如何简化它.下面再次是要求

I know there is Polymorphic Relation but I cant wrap my head around it. Please help how i can simplify it. once again below are the requirements

• 用户可以关注许多帖子
• 用户可以遵循许多类别
• 用户可以关注许多用户

• User can follow many Posts
• User can follow many Category
• User can follow many User

推荐答案

您可以使用

You can use morphedByMany to create polymorphic many to many relations. Instead of having separate *_follows tables, you can have a single followables table with the following schema:

user_id           int      # user_id that is following something
followable_id     int      # id of the thing that is being followed
followable_type   string   # type of the thing that is being followed

这是一个示例实现:

/*
 * This function gets the followers of this entity. The
 * followable_id in the followables relation would be
 * the id of this entity. 
 */
function followers() {
    return $this->morphToMany('App\User', 'followable');
}

用户模型

/*
 * Gets the list of users that are followed by this user.
 */
function users() {
    return $this->morphedByMany('App\User', 'followable');
}

/*
 * Gets the list of posts that are followed by this user.
 */
function posts() {
    return $this->morphedByMany('App\User', 'followable');
}

/*
 * Gets the list of categories that are followed by this user.
 */
function categories() {
    return $this->morphedByMany('App\User', 'followable');
}

请注意，在这种情况下，User会同时被变体和变体变为，从而创建了一个自引用的多对多关系.

Note that in this case, a User is both morphed by many and morphed to many, creating a self-reference many to many relationship.

您创建的每个新的 followable 实体，都需要向该实体添加followers()函数，并与Users实体对应的逆关系.您可以定义一个包含该函数的Followable特征，只需将use Followable;添加到您添加的新实体中即可.

Every new followable entity you create, you will need to add the followers() function to that entity, and a corresponding inverse relation to the Users entity. You could define a Followable trait containing that function, and simply add use Followable; to the new entity you add.

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