Question

我正在创建一个应用程序，允许用户记录锻炼和练习，练习作为我的锻炼表单中的嵌套模型。

routes.rb中：

 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

在我的 workouts_controller.rb ：

中

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

在我的锻炼/ _form.html.erb ：

中

<%= 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 %>

我遇到问题让fields_for按照文档（http://edgeapi.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html#method-i-fields_for）的规定工作。

它表示如果模型是一对多关联，您应该能够传递到fields_for你的模型的复数版本。这在我的锻炼＃new action中运行良好，但在我的锻炼#edit中，我必须传入单一化版本（：exercise）才能显示对象的当前属性值（锻炼）。文档说：

通常只需传递模型的名称即可简化此操作 object to fields_for - ...在这种情况下，if：permission也会发生是实例变量@permission的名称，初始状态为输入字段将反映该变量属性的值 @ permission.admin。

传递：exercise到fields的练习不会将属性保存到数据库，而传递：exercise到fields_for会将其保存到数据库中，但不会在编辑操作中显示当前属性值。

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

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

使用fields_for：exercise

<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#create：

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)

注意未经许可的参数：练习。

有谁知道为什么会这样？我很难过。任何帮助都会超级棒。如果没有人有任何想法，我可能会尝试创建一个新的rails 4应用程序并在那里测试这些关联。

Answer 1

在rails 4应用程序中，您需要切换质量分配策略以使用强参数。这意味着从模型中删除attr_accessible并将它们放在控制器中。这就是你的日志在第6-7行告诉你的内容。

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

有很多资源可以获得有关强参数的更多信息 - 这里是来自Ryan Bates的资料：http://railscasts.com/episodes/371-strong-parameters

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

1 个答案: