Implement playlists/show in API

app/controllers/api/playlists_controller.rb

@@ -4,6 +4,10 @@ module API
       @playlists = Playlist.all
     end
 
+    def show
+      @playlist = Playlist.find(params[:id])
+    end
+
     def create
       @playlist = current_user.playlists.build playlist_params
       @playlist.save

app/views/api/playlists/show.rabl

@@ -0,0 +1,4 @@
+object @playlist
+
+attribute :id
+attribute :name