我应该如何定义我的多态表？

Question

我有一个帖子表，可以是视频帖子、文字帖子或图片帖子，并且帖子属于一个组。我认为多态关系是正确的方法，但我的表看起来有点奇怪。

我的帖子表：

+---------------+------------------+------+-----+---------------------+----------------+
| Field         | Type             | Null | Key | Default             | Extra          |
+---------------+------------------+------+-----+---------------------+----------------+
| id            | int(10) unsigned | NO   | PRI | NULL                | auto_increment |
| postable_id   | int(10) unsigned | NO   |     | NULL                |                |
| postable_type | varchar(255)     | NO   |     | NULL                |                |
| group_id      | int(10) unsigned | NO   | MUL | NULL                |                |
| upvotes       | int(10) unsigned | NO   |     | 0                   |                |
| downvotes     | int(10) unsigned | NO   |     | 0                   |                |
| created_at    | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
| updated_at    | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
+---------------+------------------+------+-----+---------------------+----------------+

text_posts 表：

+------------+------------------+------+-----+---------------------+----------------+
| Field      | Type             | Null | Key | Default             | Extra          |
+------------+------------------+------+-----+---------------------+----------------+
| id         | int(10) unsigned | NO   | PRI | NULL                | auto_increment |
| title      | varchar(130)     | NO   |     | NULL                |                |
| body       | text             | NO   |     | NULL                |                |
| created_at | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
| updated_at | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
+------------+------------------+------+-----+---------------------+----------------+

video_posts 表：

+------------+------------------+------+-----+---------------------+----------------+
| Field      | Type             | Null | Key | Default             | Extra          |
+------------+------------------+------+-----+---------------------+----------------+
| id         | int(10) unsigned | NO   | PRI | NULL                | auto_increment |
| title      | varchar(130)     | NO   |     | NULL                |                |
| path       | varchar(255)     | NO   |     | NULL                |                |
| body       | varchar(255)     | YES  |     | NULL                |                |
| created_at | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
| updated_at | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
+------------+------------------+------+-----+---------------------+----------------+

picture_posts 表：

+-------------+------------------+------+-----+---------------------+----------------+
| Field       | Type             | Null | Key | Default             | Extra          |
+-------------+------------------+------+-----+---------------------+----------------+
| id          | int(10) unsigned | NO   | PRI | NULL                | auto_increment |
| path        | varchar(255)     | NO   |     | NULL                |                |
| body        | varchar(255)     | YES  |     | NULL                |                |
| is_external | tinyint(1)       | NO   |     | NULL                |                |
| created_at  | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
| updated_at  | timestamp        | NO   |     | 0000-00-00 00:00:00 |                |
+-------------+------------------+------+-----+---------------------+----------------+

我查看了来自 laravel.com 的示例。它指出“多态关系允许一个模型在一个关联上属于多个其他模型。”但在这种情况下，我的“帖子”不应该属于“视频帖子”或“文本帖子”等。而是'视频帖子'或类似内容应属于'帖子'。如何改进我的表格？？

Answer 1

貌似Many To Many多态关系：

根据您有问题的表，您的公用表是posts，并且您希望在其他三个不同实体（表）之间建立关系，换句话说，所有三个表（texts、videos 和 pictures）都将共享posts 表，例如，您有三个这样的表（每个表都以id 为Primary Key）：

texts  table   |
videos table   |--- posts
pictures table |

每个表都应该与posts 表相关，因此您需要三个单独的表和每个like 的三个模型；

Table                  | Other Personal Fields   |  Model
------------------------------------------------------------
texts (with id PK)     | title, body             |  Text
videos (with id PK)    | title, path, body       |  Video
pictures (with id PK)  | path, body, is_external |  Picture

主/公用表是posts，把所有公用字段都放在这个表里：

id (PK)       |
group_id      |
upvotes       |--- These are common/sharable fields by other three models
downvotes     |
created_at    |
updated_at    |

第四张表postablesPOST 与所有其他人（文本、视频和图片）之间的关系：

post_id       | Always id of posts table
              | These two fields will build relation
postable_id   | id of texts or videos or pictures
postable_type | The model/type: Text/Video/Picture

与Post相反的三个模型：

// Text: In the postables table postable_id
// will be texts_id and type will be Text for text_post
class Text extends Eloquent {
    public function posts()
    {
        return $this->morphToMany('Post', 'postable');
    }
}

// Video: in the postables table postable_id will
// be videos_id and type will be Video for video_post
class Video extends Eloquent {
    public function posts()
    {
        return $this->morphToMany('Post', 'postable');
    }
}

// Picture: in the postables table postable_id will
// be pictures_id and type will be Picture for picture_post
class Picture extends Eloquent {
    public function posts()
    {
        return $this->morphToMany('Post', 'postable');
    }
}

Post 模型：

class Post extends Eloquent {

    public function texts()
    {
        return $this->morphedByMany('Text', 'postable');
    }

    public function videos()
    {
        return $this->morphedByMany('Video', 'postable');
    }

    public function pictures()
    {
        return $this->morphedByMany('Picture', 'postable');
    }
}

postables 表中的数据可能是这样的：

post_id | postable_id  |  postable_type
---------------------------------------
   1    |      1       |      Text      // In postable_id 1 is id of texts table
   1    |      1       |      Video     // In postable_id 1 is id of videos table
   1    |      1       |      Picture   // In postable_id 1 is id of pictueres table
   2    |      3       |      Text      // In postable_id 3 is id of texts table

用法：

$post = Post::find(1);
$postsHastTextPosts = $post->texts();

反向使用（Text）：

$text = Text::find(1);
$text->posts()->first()->group_id;
$text->posts()->first()->upvotes;

反向使用（Video）：

$vdo = Video::find(1);
$vdo->posts()->first()->group_id;
$vdo->posts()->first()->upvotes;

反向使用（Picture）：

$picture = Picture::find(1);
$picture->posts()->first()->group_id;
$picture->posts()->first()->upvotes;

这可以使用many to many 多态关系来完成。所有三种模型（Text、Video 和 Picture）都可以共享相同的公共POST 属性，这意味着所有三种类型的模型都可以属于一组 (group_id)。

在这个使用一个表 (postables) 的 many-to-many polymorphic 关系中，三个单独的 pivot 表（post_text、post_picture 和 post_video）已被排除在外。