Rails 4.0测试版，fields_for不接受一对多关联中的复数model_name

Question

我正在创建一个应用程序，允许用户记录锻炼和锻炼，锻炼作为一个嵌套模型在我的锻炼表单。

routes.rb:

 resources :users do 
    resources :workouts
  end

workouts.rb:

attr_accessible :name, :exercises_attributes
has_many :exercises
belongs_to :user
accepts_nested_attributes_for :exercises, :allow_destroy => true

exercise.rb:

attr_accessible :name, :weight, :reps
belongs_to :workout

在my workouts_controller.rb:

def create
  @workout = @user.workouts.new(workout_params)
  @exercise = @workout.exercises.new(params[:workout][:exercise])
respond_to do |format|
  if @workout.save && @exercise.save
    //...etc

我在<<p> strong>训练/_form.html.erb :

<%= form_for [@user, @workout], builder: LabeledFormBuilder do |f| %>
    <%= f.text_field :name %>
        <%= f.fields_for :exercises do |builder| %>
            <%= builder.text_field :name %>
            <%= builder.text_field :weight %>
            <%= builder.text_field :reps %>
        <% end %>
        <%= f.submit %>
<% end %>

我有麻烦得到fields_for工作规定的文档(http://edgeapi.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-fields_for)。

它表示，如果模型处于一对多关联中，您应该能够将模型的复数版本传递给fields_。这在我的workout #new action中工作得很好，但是在我的workout #edit中，为了显示对象(锻炼)的当前属性值，我必须传入单数版本(:exercise)。医生说:

通常，这可以通过只传递模型的名称来简化对象到fields_for -…在这种情况下，if:permission也发生在是实例变量@permission的名称，是的初始状态输入字段将反映该变量的属性值@permission.admin。

将:exercises传递给fields_for不会将属性保存到数据库，而将:exercise传递给fields_for会将其保存到数据库，但不会在编辑操作中显示当前属性值。

在训练#new和#edit中:with fields_for:exercise

<div class="field"><input id="workout_exercise_name" name="workout[exercise][name]" placeholder="name" type="text" /></div>

with fields_for:exercises

<div class="field"><input id="workout_exercises_attributes_0_name" name="workout[exercises_attributes][0][name]" placeholder="name" type="text" /></div>

最后，我在我的开发日志中有以下内容:

Started POST "/users/5/workouts" for 127.0.0.1 at 2013-04-07 14:13:45 -0400
Processing by WorkoutsController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"a98ozlUWDtZc49v/PfFds/V0S56R2Y73HsxW6+wjYWI=", "workout"=>{"name"=>"test", "exercise"=>{"name"=>"lunge", "weight"=>"30", "reps"=>"20", "_destroy"=>""}}, "commit"=>"Create Workout", "user_id"=>"5"}
  User Load (0.4ms)  SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", "5"]]
  User Load (0.4ms)  SELECT "users".* FROM "users" WHERE "users"."auth_token" = 'dHhQQSEecDOetjh-ZROpmw' LIMIT 1
Unpermitted parameters: exercise
WARNING: Can't mass-assign protected attributes for Exercise: _destroy
    app/controllers/workouts_controller.rb:32:in `create'
   (0.2ms)  BEGIN
  SQL (0.8ms)  INSERT INTO "workouts" ("created_at", "name", "updated_at", "user_id") VALUES ($1, $2, $3, $4) RETURNING "id"  [["created_at", Sun, 07 Apr 2013 18:13:45 UTC +00:00], ["name", "test"], ["updated_at", Sun, 07 Apr 2013 18:13:45 UTC +00:00], ["user_id", 5]]
  SQL (0.6ms)  INSERT INTO "exercises" ("created_at", "name", "reps", "updated_at", "weight", "workout_id") VALUES ($1, $2, $3, $4, $5, $6) RETURNING "id"  [["created_at", Sun, 07 Apr 2013 18:13:45 UTC +00:00], ["name", "lunge"], ["reps", 20], ["updated_at", Sun, 07 Apr 2013 18:13:45 UTC +00:00], ["weight", 30], ["workout_id", 64]]
   (0.6ms)  COMMIT
   (0.4ms)  BEGIN
   (0.2ms)  COMMIT
Redirected to http://localhost:3000/users/5/workouts
Completed 302 Found in 21ms (ActiveRecord: 3.5ms)

notice 不允许的参数:exercise.

有人知道为什么会这样吗?我被难住了。任何帮助都会非常棒。如果没有人有任何想法，我可能会尝试创建一个新的rails 4应用程序并测试这些关联。

Answer 1

在rails 4应用程序中，你需要切换你的质量分配策略来使用强参数。这意味着从模型中删除attr_accessible并将它们放在控制器中。这是日志在第6-7行告诉你的。

使用嵌套属性，控制器中的workout_params将看起来像这样:

private
def workout_params
  params.require(:workout).permit(
    :id,
    :next_attribute,
    :next_attribute,
    exercises_attributes: [
    :id,
    :next_attribute,
    :next_attribute
  ])
end

关于强参数的更多信息有各种各样的资源，这里有一个来自Ryan Bates: http://railscasts.com/episodes/371-strong-parameters