如何访问模型 hasMany 与 where 条件的关系? [英] How to access model hasMany Relation with where condition?

问题描述

我使用关系的条件/约束创建了一个模型游戏，如下所示:

I created a model Game using a condition / constraint for a relation as follows:

class Game extends Eloquent {
    // many more stuff here

    // relation without any constraints ...works fine 
    public function videos() {
        return $this->hasMany('Video');
    }

    // results in a "problem", se examples below
    public function available_videos() {
        return $this->hasMany('Video')->where('available','=', 1);
    }
}

以某种方式使用它时:

$game = Game::with('available_videos')->find(1);
$game->available_videos->count();

一切正常，因为角色是结果集合.

everything works fine, as roles is the resulting collection.

我的问题:

当我尝试在不急切加载的情况下访问它时

when I try to access it without eager loading

$game = Game::find(1);
$game->available_videos->count();

抛出异常，因为它说在非对象上调用成员函数 count()".

an Exception is thrown as it says "Call to a member function count() on a non-object".

使用

$game = Game::find(1);
$game->load('available_videos');
$game->available_videos->count();

工作正常，但对我来说似乎很复杂，因为我不需要加载相关模型，如果我不在我的关系中使用条件.

works fine, but it seems quite complicated to me, as I do not need to load related models, if I do not use conditions within my relation.

我错过了什么吗?如何确保在不使用预先加载的情况下可以访问 available_videos?

Have I missed something? How can I ensure, that available_videos are accessible without using eager loading?

对于任何感兴趣的人，我也在 http://forums.laravel.io/viewtopic 上发布了这个问题.php?id=10470

For anyone interested, I have also posted this issue on http://forums.laravel.io/viewtopic.php?id=10470

推荐答案

以防万一其他人遇到同样的问题.

Just in case anyone else encounters the same problems.

请注意，关系必须是驼峰式的.所以在我的例子中 available_videos() 应该是 availableVideos().

Note, that relations are required to be camelcase. So in my case available_videos() should have been availableVideos().

你可以很容易地找到调查 Laravel 源代码:

You can easily find out investigating the Laravel source:

// IlluminateDatabaseEloquentModel.php
...
/**
 * Get an attribute from the model.
 *
 * @param  string  $key
 * @return mixed
 */
public function getAttribute($key)
{
    $inAttributes = array_key_exists($key, $this->attributes);

    // If the key references an attribute, we can just go ahead and return the
    // plain attribute value from the model. This allows every attribute to
    // be dynamically accessed through the _get method without accessors.
    if ($inAttributes || $this->hasGetMutator($key))
    {
        return $this->getAttributeValue($key);
    }

    // If the key already exists in the relationships array, it just means the
    // relationship has already been loaded, so we'll just return it out of
    // here because there is no need to query within the relations twice.
    if (array_key_exists($key, $this->relations))
    {
        return $this->relations[$key];
    }

    // If the "attribute" exists as a method on the model, we will just assume
    // it is a relationship and will load and return results from the query
    // and hydrate the relationship's value on the "relationships" array.
    $camelKey = camel_case($key);

    if (method_exists($this, $camelKey))
    {
        return $this->getRelationshipFromMethod($key, $camelKey);
    }
}

这也解释了为什么我的代码可以工作，每当我之前使用 load() 方法加载数据时.

This also explains why my code worked, whenever I loaded the data using the load() method before.

无论如何，我的示例现在可以正常运行，并且 $model->availableVideos 总是返回一个集合.

Anyway, my example works perfectly okay now, and $model->availableVideos always returns a Collection.

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