我使用多态关联，跟踪我的项目注释。一切都非常简单的东西。

I am using polymorphic associations to track Comments in my project. All very straight forward stuff.

我的问题是在查询基础上，多态关联，并从评价模型回到它的主人加入。

The problem I have is in querying based on the polymorphic association and joining from the Comment model back to it's owner.

所以...

我有一个注释模式

class Comment < ActiveRecord::Base
  belongs_to :commentable, :polymorphic => true
end

和一个ForumTopics方式：

And a ForumTopics mode:

class ForumTopic < ActiveRecord::Base
  has_many :comments, :as => :commentable
end

我有几个其他的commentable模式，并不重要，现在。 所有这些工作的。

I have several other "commentable" models that aren't important right now. All of this works.

我所试图做的是找到所有属于ForumTopic与指定条件的意见（在这种情况下，'特色'==真）。

What I am trying to do is find all of the Comments that belong to a ForumTopic with a specified condition (in this case, 'featured' == true).

当我尝试使用取景器的加入模型：

When I try and use a finder to join the models:

@comments = Comment.find(:all 
            :joins => :commentable
            :conditions => ["forum_topics.featured = ? ", true] 
            )

我收到以下错误：

I receive the following error:

不能急于加载多态性关联：commentable 的

使用AR有语法：

@comments = Comment.find(:all 
            :include => :forum_topics
            :conditions => ["forum_topics.featured = ? ", true] 
            )

收益：

协会命名为forum_topics未找到;也许你拼错了？的

如果我试图加入一个表名，而不是协会名称（字符串而不是符号）：

If I try and join with a table name instead of the association name (string instead of symbol):

@comments = Comment.find(:all,
            :joins => "forum_topics",
            :conditions => ["forum_topics.featured = ? ", true] 
            )

我看到：

Mysql的::错误：未知的表格'评论'：选择意见的自评forum_topics WHERE（forum_topics.featured = 1）*

Mysql::Error: Unknown table 'comments': SELECT comments. FROM comments forum_topics WHERE (forum_topics.featured = 1 )*

（你可以在这里看到，基础查询语法是完全关闭和连接全部丢失）。

(You can see here that the syntax of the underlying query is totally off and the join is missing altogether).

不知道我在做什么，甚至可能的，还有其他的方法来达到要求的结果，但看起来它的应的是可行的。

Not sure if what I am doing is even possible, and there are other ways to achieve the required result but it seems like it should be doable.

任何想法？ 什么我失踪？

Any ideas? Anything I am missing?

推荐答案

哎呀！

我想我找到了问题。

在通过加入：

@comments = Comment.find(:all,
        :joins => "forum_topics",
        :conditions => ["forum_topics.featured = ? ", true] 
        )

您需要整个加盟！

:joins => "INNER JOIN forum_topics ON forum_topics.id = comments.commentable_id",

请参阅不断真棒： http://guides.rubyonrails.org/active_record_querying.html#joining-tables