Question

我有两个通过第三个连接的模型：

Playlist has_many :song_in_playlists, :dependent => :destroy
         has_many :songs, :through => :song_in_playlists

Song has_many :song_in_playlists, :dependent => :destroy
     has_many :playlists, :through => :song_in_playlists

song_in_playlist表只列出playlist_id，song_id以及track_number。

当调用/playlists/1.json时，我想获得一个包含播放列表属性的json哈希，并且里面有另一个哈希，其中包含歌曲（如/songs.json加track_number来自song_in_playlists表条目。）

根据the Rails API，我应该能够做到以下几点：

  def show
    @playlist = Playlist.find(params[:id])
    [...]
      respond_to do |format|
        format.html # show.html.erb
        format.json { render json: @playlist.as_json(
                           :include => { :song_in_playlists => { 
                              :only => :track_number, :include => :songs { 
                                 :except => [:dropbox_link, :local_path] } } } 
                            ) }
      end
    end
  end

但是，我得到的是以下内容：

/home/sloth/audiomixer/app/controllers/playlists_controller.rb:30: syntax error, unexpected '{', expecting '}'
            :only => :track_number, :include => :songs { 
                                                        ^
/home/sloth/audiomixer/app/controllers/playlists_controller.rb:31: syntax error, unexpected '}', expecting keyword_end
              :except => [:dropbox_link, :local_path] } } } 
                                                         ^
/home/sloth/audiomixer/app/controllers/playlists_controller.rb:103: syntax error, unexpected $end, expecting keyword_end

所以我尝试了一点点复杂性，调用

format.json { render json: @playlist.as_json( 
                                :include => song_in_playlists { 
                                   :only => :track_number } ) }

但是我遇到了类似的错误。一旦我在括号之间添加任何括号，Rails就会抱怨，尽管API文档反过来说明了。

我真的不知道该怎么办:(

PS：Ruby 1.9.3，Rails 3.2.13

---编辑--- 好吧，我真的不知道为什么，但我得到了这个产生预期的输出：

format.json { render json: @playlist.as_json( 
                    :include => { :song_in_playlists => { 
                       :include => :song, :only => :track_number } } ) }

但是，当我尝试在{ :except => [:dropbox_link, :local_path] }和:song之间添加, :only时，我再次遇到相同的错误..

Answer 1

这只是部分关于rails

:include => song_in_playlists {:only => :track_number}

只是无效的ruby语法

这应该是

:include => {:song_in_playlists => {:only => :track_number}}

每次键都是关联名称（song_in_playlists），值是包含一个或多个键:only，:except或:include

的哈希值

如果你想更改json中歌曲表中的属性，那么你需要

format.json { render json: @playlist.as_json( 
                :include => { :song_in_playlists => { 
                   :include => :song, :only => :track_number } } ) }

并将:song替换为描述您要对歌曲做什么的哈希，例如

format.json { render json: @playlist.as_json( 
                :include => { 
                  :song_in_playlists => { 
                    :include => {
                      :song => {
                        :except => [:dropbox_link, :local_path]
                      }
                    }, 
                    :only => :track_number 
                  } 
                 })}

使用多级别时，as_json中的语法错误：include

1 个答案: