在 Laravel 6 中，设置与获取同一个模型的自关联

1、表存在 2 个字段：original_theme_id、theme_id，字段 original_theme_id 的值源自于表中的另一条记录的 theme_id。如图1

图1

2、在模型中设置一对一的反向关联。代码实现如下

    /**
     * 获取此主题安装所属原始的主题安装
     * @return BelongsTo
     */
    public function originalThemeInstallation()
    {
        return $this->belongsTo('Modules\ThemeStoreDB\Entities\ThemeInstallation', 'original_theme_id', 'theme_id');
    }

3、获取关联属性的代码实现，生成的 SQL

        $themeInstallation = ThemeInstallation::find(345);
        print_r($themeInstallation->originalThemeInstallation);
        exit;

select
  *
from
  `theme_installation`
where
  `theme_installation`.`theme_id` = '96b1c8b9-5b18-4760-9e26-50ab009ac011'
  and `theme_installation`.`deleted_at` is null
limit
  1

4、打印结果，符合预期

Modules\ThemeStoreDB\Entities\ThemeInstallation Object
(
    [table:protected] => theme_installation
    [attributes:protected] => Array
        (
            [id] => 35
            [theme_store_theme_id] => 21
            [original_theme_id] => 
            [theme_id] => 96b1c8b9-5b18-4760-9e26-50ab009ac011
            [original_wp_theme_id] => 0
            [wp_theme_id] => 6
            [theme_name] => brooklyn
            [theme_custom_name] => brooklyn 6 2
            [type] => 1
            [role] => unpublished
            [processing] => 0
            [processing_failed] => 0
            [created_at] => 2022-07-04 02:53:29
            [updated_at] => 2022-12-09 03:04:36
            [deleted_at] => 
        )

)