laravel - 为什么 eloquent 在 FK 名字后面加下划线？

Question

我之间存在多对多关系

extensiontables_registry

和

Ad_groups

数据透视表为extensiontables_registryxad_groups

现在我有这个代码:

$permittedTables = extensiontables_registry::has("ad_groups")->get();

我想看看这会给我带来什么，所以我这样做:

log::info($permittedTables);

我收到此错误:

[2020-05-11 07:32:23] local.ERROR: PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'extensiontables_registryxad_groups.extensiontables__registry_id' in 'where clause' in E:\aether-backend\vendor\illuminate\database\Connection.php:331

据我所知，laravel/eloquent 会自动向 extensiontables_registryxad_groups 数据透视表上的 extensiontables_registry_id 列添加下划线。为什么要这样做？我该如何预防？

这三个表目前如下所示:

扩展表注册表:

+----+-----------------------+------------+------------+
| id | extensiontable_name   | created_at | updated_at |
+----+-----------------------+------------+------------+
|  1 | extensiontable_itc    | NULL       | NULL       |
|  2 | extensiontable_sysops | NULL       | NULL       |
|  4 | test                  | NULL       | NULL       |
+----+-----------------------+------------+------------+

extensiontables_registryxad_groups:

+-----------------------------+-------------+------------+------------+
| extensiontables_registry_id | ad_group_id | created_at | updated_at |
+-----------------------------+-------------+------------+------------+
|                           1 |           8 | NULL       | NULL       |
|                           2 |           8 | NULL       | NULL       |
+-----------------------------+-------------+------------+------------+

广告组:

+----+------------------------------------+---------------------+---------------------+
| id | name                               | created_at          | updated_at          |
+----+------------------------------------+---------------------+---------------------+
|  1 | test16                             | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  2 | test15                             | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  3 | test14                             | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  4 | test13                             | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  5 | test12                             | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  6 | test11                             | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  7 | test10                             | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  8 | test9                              | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
|  9 | test8                              | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
| 10 | test7                              | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
| 11 | test6                              | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
| 12 | test5                              | 2020-02-26 09:30:21 | 2020-02-26 09:30:21 |
| 13 | test4                              | 2020-03-16 13:27:24 | 2020-03-16 13:27:24 |
| 14 | test3                              | 2020-03-16 13:27:24 | 2020-03-16 13:27:24 |
| 15 | test2                              | 2020-03-16 13:27:24 | 2020-03-16 13:27:24 |
| 16 | test                               | 2020-03-16 13:27:24 | 2020-03-16 13:27:24 |
+----+------------------------------------+---------------------+---------------------+

所以这个查询肯定应该有一些结果，对吧？另外，查询本身运行，但是当我尝试记录它时，出现上述错误。

为了完整起见，以下是定义 eloquent 模型的类:

AD_Group.php:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Ad_group extends Model
{
  /**
   * The attributes that are mass assignable.
   *
   * @var array
   */
  protected $fillable = [
    'name'
  ];

  /**
   * Hides pivot from return queries.
   *
   * @var array
   */
  protected $hidden = [
    'pivot'
  ];

  /**
   * Many-To-Many relationship with User-Model.
   */
  public function Ad_users()
  {
    return $this->belongsToMany('App\Ad_user', 'Ad_usersxad_groups', 'Ad_group_id', 'Ad_user_id');
  }

  public function extensiontables()
  {
    return $this->belongsToMany('App\extensiontables_registry', 'extensiontables_registryxad_groups');
  }

}

和Extensiontables_registry.php:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Extensiontables_Registry extends Model
{

  /**
 * The table associated with the model.
 *
 * @var string
 */
 protected $table = 'Extensiontables_Registry';

  /**
   * The attributes that are mass assignable.
   *
   * @var array
   */
  protected $fillable = [
    'extensiontable_name'
  ];



  /**
   * Many-To-Many relationship with User-Model.
   */
  public function Ad_groups()
  {
    return $this->belongsToMany('App\Ad_group', 'extensiontables_registryxad_groups');
  }
}

Answer 1

好吧，我自己找到了答案: https://laracasts.com/discuss/channels/laravel/custom-name-and-foreign-key-for-manytomany-relationship

TL/DR: Laravel/Eloquent 在“猜测”数据透视表上我的 FK 属性的名称时遇到问题。所以我必须明确地定义它们。请参阅此处的 laravel 文档: https://laravel.com/docs/master/eloquent-relationships#many-to-many

“除了自定义连接表的名称之外，您还可以通过向belongsToMany方法传递附加参数来自定义表上键的列名称。第三个参数是模型的外键名称您正在定义关系，而第四个参数是您要加入的模型的外键名称:

return $this->belongsToMany('App\Role', 'role_user', 'user_id', 'role_id');

"

就我而言，在extensiontables_registry.php上我需要这个:

  public function Ad_groups()
  {
    return $this->belongsToMany('App\Ad_group', 'extensiontables_registryxad_groups', 'extensiontables_registry_id', 'ad_group_id');
  }

在 AD_Group.php 上我需要这个:

  public function extensiontables()
  {
    return $this->belongsToMany('App\extensiontables_registry', 'extensiontables_registryxad_groups', 'ad_group_id', 'extensiontables_registry_id');
  }