无法在雄辩的多态关系中获取数据

Question

我正在使用 polymorphic relations 构建评论系统，看起来一切正常。

这是我的帖子模型

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;

class Posts extends Model
{
    public $primaryKey = 'pid';
    public $timestamps = false;

    public function author()
    {
        return $this->belongsTo('App\User', 'p_author_id');
    }

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

}

这是我的评论模型

<?php

namespace App;
use Illuminate\Database\Eloquent\Model;

class Comment extends Model
{
    public function commentable()
    {
        return $this->morphTo();
    }

    public function user()
    {
        return $this->belongsTo('App\User');
    }

    public function posts()
    {
        return $this->belongsTo('App\Posts', 'pid');
    }

}

现在的问题是，

$pin = Posts::find($pin_id);

没有 returning 任何与 post 相关的评论！请注意，它有作者实体但没有评论。

print_r($pin->toArray());

只会return下面的数组，

Array
(
    [pid] => 17
    [p_title] => Hello World?
    [p_content] => How are you earth?
    [p_author_id] => 4
    [p_created_at] => 2016-09-15 17:18:16
    [p_updated_at] => 2016-09-15 17:18:16
    [comments_count] => 0
    [votes] => 0
    [author] => Array
        (
            [id] => 4
            [name] => Human
            [email] => human@mail.com
            [created_at] => 2016-09-15 17:18:00
            [updated_at] => 2016-09-15 17:20:05
        )

)

为什么此处缺少评论实体？谢谢:)

Answer 1

尝试 Eager loading 如下：

$pin = Posts::with('comments')->find($pin_id);

并在数据库的 commentable_type 列中使用 App\Posts 而不是 Posts。那是因为：（引用自laravel documentation）

The commentable_type column is how the ORM determines which "type" of owning model to return when accessing the commentable relation.

另请关注naming convention for models。

无法在雄辩的多态关系中获取数据

Unable to fetch data in Elequent Polymorphic Relationship

php

mysql

laravel-5

laravel-5.3