語法錯誤：包括

Question

我已經得到了通過第三個連接兩種型號：

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 

的song_in_playlist表只列出了playlist_id，song_id，以及一個track_number。

當調用/playlists/1.json，我想獲得一個JSON哈希保存播放列表的屬性和具有內另一哈希值，其中包含的歌曲（如/songs.json加上track_number從song_in_playlists表項）。

據the Rails API，我應該能夠做到這一點執行以下操作：

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 

不過，我做什麼，得到的是如下：

/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 

於是，我就有點不太複雜，打電話

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

但我收到類似的錯誤。只要我在括號中加上括號，Rails就會抱怨，儘管API文檔說明了相反的情況。

我真的不知道該怎麼再嘗試了:(

PS：紅寶石1.9.3，導軌3.2.13

---編輯--- 好吧，我不噸真的知道爲什麼，但我得到這個產生預期的輸出：試圖在:song和, :only之間，我又收到同樣的錯誤添加{ :except => [:dropbox_link, :local_path] }當

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

然而，..

Answer 1

這只是部分約軌

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

僅僅是不正確的Ruby語法

這應該是

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

每一次，關鍵是組織名稱（song_in_playlists）並且該值是包含一個或多個密鑰的散列值:only,:except或:include

如果你想改變的歌曲表什麼屬性都在JSON，那麼你需要採取

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

，並描述你想要的歌曲做一個哈希更換:song，例如

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