Use new "strong parameters" from rails4

app/controllers/api/playlists_controller.rb

@@ -7,8 +7,14 @@ module API
     end
 
     def create
-      @playlist = current_user.playlists.build(params[:playlist].slice(:name))
+      @playlist = current_user.playlists.build(playlist_params)
       @playlist.save
     end
+
+    private
+
+    def playlist_params
+      params.require(:playlist).permit(:name)
+    end
   end
 end

app/controllers/playlists_controller.rb

@@ -8,7 +8,7 @@ class PlaylistsController < ApplicationController
   end
 
   def create
-    @playlist = current_user.playlists.build(params[:playlist])
+    @playlist = current_user.playlists.build(playlist_params)
     if @playlist.save
       redirect_to action: 'index'
     else
@@ -22,10 +22,16 @@ class PlaylistsController < ApplicationController
 
   def update
     @playlist = Playlist.find(params[:id])
-    if @playlist.update_attributes params[:playlist]
+    if @playlist.update_attributes playlist_params
       redirect_to action: 'index'
     else
       render action: 'edit'
     end
   end
+
+  private
+
+  def playlist_params
+    params.require(:playlist).permit(:name)
+  end
 end

app/controllers/tracks_controller.rb

@@ -8,11 +8,17 @@ class TracksController < ApplicationController
   end
 
   def create
-    @track = Track.new params[:track]
+    @track = Track.new track_params
     if @track.save
       redirect_to @track
     else
       render :new
     end
   end
+
+  private
+
+  def track_params
+    params.require(:track).permit(:name, :file)
+  end
 end

app/controllers/users_controller.rb

@@ -6,7 +6,7 @@ class UsersController < ApplicationController
   end
 
   def create
-    @user = User.new(params[:user])
+    @user = User.new(user_params)
     if !@user.save
       render :new
     else
@@ -14,4 +14,10 @@ class UsersController < ApplicationController
       redirect_to :root
     end
   end
+
+  private
+
+  def user_params
+    params.require(:user).permit(:email, :password, :password_confirmation)
+  end
 end