Rails4 HAS_MANY通过与参数 [英] Rails4 has_many through with parameters

问题描述

我通过协会的has_many如下：

I have a has_many through association as follows:

has_many :bookmarks, -> {where('actions.bookmark=true')},
    :through => :actions,
    :source => :object

我想要做的是延长上述通过类别书签的对象。类似如下：

what I'd like to do is to extend the above to pass categories for the objects bookmarked. Something like the following:

has_many :bookmarks, -> (category) {where('actions.bookmark=true and objects.category=?', category)},
    :through => :actions,
    :source => :object

我希望它会允许我这样做，例如 user.bookmarks查询（纸）。然而，当我尝试了上面，类呈现的＃＆LT的价值;用户：0x000001017f2090＆GT; （基本上用户在上面的调用），我似乎不能够调用一个简单的字符串的关联。

I was hoping it would allow me to do queries such as user.bookmarks("papers"). However, when I try the above, category takes on the value of #<User:0x000001017f2090> (basically user in the call above) and I don't seem to be able to call the association with a simple string.

在如何能够实现任何建议？非常感谢。

Any suggestion on how this could be achieved? Thanks very much.

推荐答案

我不认为这可以在的has_many 调用来实现。我只希望在我的用户定义一个实例方法类来获得该功能：

I don't think this can be achieved in the has_many call. I'd just define an instance method in my User class to get that functionality:

def bookmarks_for_category(category)
  bookmarks.includes(:objects).where('objects.category = ?', category)
end

不知道这个方法的实现，但问题是，我不认为你可以有一个的has_many 接受参数。

另一件事你可以看看是范围。在这种情况下，你可能要定义你的收藏模型 for_category 范围，允许这样的：

Another thing you could look into is scopes. In this case you may want to define a for_category scope on your Bookmark model, allowing something like:

user.bookmarks.for_category('papers')

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