Laravel学习笔记（22）模型关系（远程一对一，远程一对多，多态一对一，多态一对多，多态多对多）

1. 远程一对一

一个帖子属于一个作者，该作者就读一所学校。帖子可通过作者访问作者所在的学校

模型关系

# App\Thread
public function authorSchool()
{
    return $this->hasOneThrough('App\School', 'App\Author');
}

# App\Thread
public function authorSchool()
{
    return $this->hasOneThrough(
        'App\School',
        'App\Author',
        'thread_id', // 作者表外键
        'author_id', // 学校表外键
        'id',        // 帖子本地键
        'id',        // 作者本地键
    );
}

查

$school = \App\Thread::find(2)->authorSchool;
$threadsWithSchool = \App\Thread::with('authorSchool')->get();

2. 远程一对多

一个帖子属于一个作者，该作者有多本书。帖子可通过作者访问作者的书

模型

# App\Thread
public function authorBook()
{
    return $this->hasManyThrough('App\Book', 'App\Author');
}

# App\Thread
public function authorBooks()
{
    return $this->hasOneThrough(
        'App\Book',
        'App\Author',
        'thread_id', // 作者表外键
        'author_id', // 书表外键
        'id',        // 帖子本地键
        'id',        // 作者本地键
    );
}

查

$books = \App\Thread::find(2)->authorBooks;
$threadsWithBooks = \App\Thread::with('authorBooks')->get();

3. 多态一对一

运营人员就一个图片，发布一篇博客或者一篇文章。

表结构

articles
    id - integer
    title - string

blogs
    id - integer
    title - string

images
    id - integer
    url - string
    imageable_id - integer
    imageable_type - string

模型

# App\Image，imageable和表字段名对应
public function imageable()
{
    return $this->morphTo();
}

# App\Blog
public function image()
{
    return $this->morphOne('App\Image', 'imageable');
}

# App\Article
public function image()
{
    return $this->morphOne('App\Image', 'imageable');
}

增

App\Blog::create(['title'=>'test'])->image()->create(['url'=>'123465'])

查

$article = App\Article::find(1);
$image= $article->image;

$articleWithImages = App\Article::with('image')->find(1);
$articlesWithImages = App\Article::with('image')->find([1, 2]);
App\Image::with('imageable')->get()->toArray();

$image = App\Image::find(1);
$imageable = $image->imageable;

4. 多态一对多

文章可以接受多条评论，视频也可以接受多条评论。

表

articles
    id - integer
    title - string
    body - text

videos
    id - integer
    title - string
    url - string

comments
    id - integer
    body - text
    commentable_id - integer
    commentable_type - string

模型结构

# App\Comment
public function commentable()
{
    return $this->morphTo();
}

# App\Video
public function comments()
{
    return $this->morphMany('App\Comment', 'commentable');
}

# App\Article
public function comments()
{
    return $this->morphMany('App\Comment', 'commentable');
}

5. 多态多对多

表

articles
    id - integer
    name - string

videos
    id - integer
    name - string

tags
    id - integer
    name - string

taggables
    tag_id - integer
    taggable_id - integer
    taggable_type - string

模型

# App\Tag
public function articles()
{
    return $this->morphedByMany('App\Article', 'taggable');
}

public function videos()
{
    return $this->morphedByMany('App\Video', 'taggable');
}
# App\Article
public function tags()
{
    return $this->morphToMany('App\Tag', 'taggable');
}

查

$video = App\Video::find(1);

foreach ($video->tags as $tag) {
    //
}
$tag = App\Tag::find(1);

foreach ($tag->videos as $video) {
    //
}
$videoWithTags = App\Video::with('tags')->find(1);
$videosWithTags = App\Video::with('tags')->find([1, 2]);
$tagWithVideos = App\Tag::with('videos')->find(1);
$tagsWithVideos = App\Tag::with('videos')->find([1, 2]);

定制

# app/Providers/AppServiceProvider.php 的boot中
use Illuminate\Database\Eloquent\Relations\Relation;

Relation::morphMap([
    'posts' => 'App\Post',  // posts 是 *_type 字段所存储的值
    'videos' => 'App\Video',
]);