Laravel 4.1：检索所有morphedBy关系的正确方法？

刚刚迁移到4.1以利用这一强大功能.
在检索单个’morphedByXxxx’关系时,一切似乎都能正常工作,但是当试图检索特定标签所属的所有模型时 – 我得到错误或没有结果.

$tag = Tag::find(45); //Tag model name = 'awesome'

//returns an Illuminate\Database\Eloquent\Collection of zero length
$tag->taggable; 

//returns Illuminate\Database\Eloquent\Relations\MorphToMany Builder class
$tag->taggable();

//returns a populated Collection of Video models
$tag->videos()->get();

//returns a populated Collection of Post models
$tag->posts()->get();

我的标签模型类像这样：

class Tag extends Eloquent
{
    protected $table = 'tags';
    public $timestamps = true;

    public function taggable()
    {
        //none of these seem to function as expected,
        //both return an instance of MorphToMany

        //return $this->morphedByMany('Tag', 'taggable');
        return $this->morphToMany('Tag', 'taggable');

        //this throws an error about missing argument 1
        //return $this->morphToMany();
    }

    public function posts()
    { 
        return $this->morphedByMany('Post', 'taggable');
    }


    public function videos()
    { 
        return $this->morphedByMany('Video', 'taggable');
    }

}

Post和Video模型如下所示：

class Post extends Eloquent
{
    protected $table = 'posts';
    public $timestamps = true;

    public function tags()
    {
        return $this->morphToMany('Tag', 'taggable');
    }

}

我能够为帖子和视频添加/删除标签,以及检索任何标签的相关帖子和视频 – 但是 – 检索标签名称为“真棒”的所有模型的正确方法是什么？

能够弄明白,很想听听有关此实施的评论.

在Tag.php中

public function taggable()
{
    return $this->morphToMany('Tag', 'taggable', 'taggables', 'tag_id')->orWhereRaw('taggables.taggable_type IS NOT NULL');
}

在调用代码时：

$allItemsHavingThisTag = $tag->taggable()
                ->with('videos')
                ->with('posts')
                ->get();