HasManyThrough 一对多关系 [英] HasManyThrough with one-to-many relationship

问题描述

我正在为一个带有如下表格的项目开发小型 CMS:

I am working on small scale CMS for a project with tables like so:

- pages
    - id
    …
- translations
    - page_id
    …
- menus
    - id
    …
- menu_page
    - menu_id
    - page_id
    …

在菜单模型中，我有这种关系:

In the Menu model I have this relationship:

function pages(){
    return $this->hasMany('Page');
}

是否可以直接在 Menu 和 Translations 之间创建一种关系，以转换为类似于此 SQL 查询的内容:

Is it possible to create a relation directly between Menu and Translations that translates to something like this SQL query:

select translations.* 
from translations
inner join menu_page on menu_page.page_id = translations.page_id
where menu_page.menu_id = ?;

谢谢！

推荐答案

你不能用内置方法做到这一点，hasManyThrough 不适用于多对多关系菜单页面.

You can't do it with builtin methods, hasManyThrough won't work with many-to-many relation menus-pages.

不过，您可以尝试以下解决方法:

However you can try a workaround like this:

public function getTranslationsAttribute()
{
    if ( ! array_key_exists('translations', $this->relations)) $this->loadTranslations();

    return $this->getRelation('translations');
}

protected function loadTranslations()
{
    $translations = Translation::join('menu_page', 'translations.page_id', '=', 'menu_page.page_id')
        ->where('menu_page.menu_id', $this->getKey())
        ->distinct()
        ->get(['translations.*','menu_id']);

    $hasMany = new IlluminateDatabaseEloquentRelationsHasMany(Translation::query(), $this, 'menu_id', 'id');

    $hasMany->matchMany(array($this), $translations, 'translations');

    return $this;
}

现在你可以这样做:

$menu = Menu::find($id);
$menu->translations; // Eloquent Collection of Translation models

所以基本上就像您使用任何关系一样.唯一的问题是你不能急切加载它.

So basically just like you would use any relation. The only trouble is that you can't eager load it.

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