如何访问“:has_many :though”使用 to_json 时连接表数据？

Question

我有三个模型（此处简化）：

class Child < ActiveRecord::Base
  has_many    :childviews, :dependent => :nullify
  has_many    :observations, :through => :childviews  
end
class Childview < ActiveRecord::Base
  belongs_to  :observation
  belongs_to  :child
end
class Observation < ActiveRecord::Base
  has_many    :childviews, :dependent => :nullify
  has_many    :children, :through => :childviews
end

我使用 Rails 的 to_json 方法将其发送到一些 JavaScript，如下所示：

render :layout => false , :json => @child.to_json(
  :include => {
    :observations => {
      :include => :photos, 
      :methods => [:key, :title, :subtitle]
    }
  },
  :except => [:password]
)

这完美地工作。通过连接表（子视图）可以很好地检索观察结果。

但是，我还想获取位于子视图连接表中的数据；特别是“needs_edit”的值。

我不知道如何在 to_json 调用中获取这些数据。

谁能帮助我吗？非常感谢。

奎斯

Answer 1

不确定，但这不应该起作用吗？

@child.to_json(
  :include => {
    :observations => {
      :include => :photos, 
      :methods => [:key, :title, :subtitle]
    },
    :childviews => { :only => :needs_edit }
  }, 
  :except => [:password]
)

编辑：
这也可能有效，因为子视图属于过度：

@child.to_json(
  :include => {
    :observations => {
      :include => { :photos, :childviews => { :only => :needs_edit } } 
      :methods => [:key, :title, :subtitle]
    }
  }, 
  :except => [:password]
)

Answer 2

感谢 Rock 的指点 - 我现在已经可以使用了！

这段代码：

@child.to_json(:include => 
  {
    :observations => {
      :include => {
        :photos => {},
        :childviews => {:only => :needs_edit}
      }, 
      :methods => [:S3_key, :title, :subtitle]
    }     
  },
  :except => [:password]
)

给了我这个输出（为了清晰起见缩写）：

{
    "child":
    {
        "foo":"bar",
        "observations":
        [
            {
                "foo2":"bar2",
                "photos":
                [
                    {
                        "foo3":"bar3",
                    }
                ],
                "childviews":
                [
                    {
                        "needs_edit":true
                    }
                ]
            }
        ]
    }
}

谢谢你，Rock！这让我很头疼。

:)

qryss