php - 无法在 Eloquent 多态关系中获取数据

Question

我正在使用 polymorphic relations 构建一个评论系统，似乎一切正常，没有任何问题。

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);

不会返回与帖子相关的任何评论!请注意，它有作者实体但没有评论。

print_r($pin->toArray());

只会返回以下数组，

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
        )

)

为什么这里缺少评论实体？谢谢:)

Answer 1

尝试 Eager loading像下面这样:

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