如何讓這個嵌套窗體創建一個新的對象

Question

我的Rails 5應用程序包括兩個模型，Activity和Timeslot。

activity.rb

class Activity < ApplicationRecord 
    belongs_to :club 
    has_many :timeslots, :dependent => :destroy 
    accepts_nested_attributes_for :timeslots 
    validates :club_id, presence: true 
    validates :name, presence: true, length: { maximum: 50 } 
end 

timeslot.rb

class Timeslot < ApplicationRecord 
    belongs_to :activity 
    validates :time_start, presence: true 
    validates :time_end, presence: true 
    validates :day, presence: true 
    #validates :activity_id, presence: true (I realised this was causing one of the errors I had) 
    default_scope -> { order(day: :asc) } 
end 

當我創建我的活動，我也想創建它的同一頁上的第一個時隙，相同的形式。

new.html.erb

<%= form_for(@activity) do |f| %> 
    <%= render 'shared/error_messages', object: f.object %> 
    <div class="field"> 
     <%= f.label :name, "Class name" %>* 
     <%= f.text_field :name, class: 'form-control' %> 

      <%= f.fields_for :timeslots do |timeslots_form| %> 
        <%= timeslots_form.label :time_start, "Start time" %> 
        <%= timeslots_form.time_select :time_start %> 

        <%= timeslots_form.label :time_end, "End time" %> 
        <%= timeslots_form.time_select :time_end %> 

        <%= timeslots_form.label :day %> 
        <%= timeslots_form.select :day, (0..6).map {|d| [Date::DAYNAMES[d], d]} %> 
      <% end %> 
    </div> 
    <%= f.submit "Create class", class: "btn btn-primary" %> 
<% end %> 

我的這個編輯/更新版本似乎是工作的罰款。

activities_controller.rb

class ActivitiesController < ApplicationController 
... 

def new 
    @activity = Activity.new 
    @activity.timeslots.build 
end 

def create 
    @activity = current_club.activities.build(activity_params) 
    #@activity.timeslots.first.activity_id = @activity.id (I thought this might solve the problem, but didn't) 
    if @activity.save 
     flash[:success] = "New class created!" 
     redirect_to activities_path 
    else 
     render 'new' 
    end 
end 

def edit 
    @activity = current_club.activities.find_by(id: params[:id]) 
    @activity.timeslots.build 
end 

def update 
    @activity = current_club.activities.find_by(id: params[:id]) 
    if @activity.update_attributes(activity_params) 
     flash[:sucess] = "Class updated!" 
     redirect_to edit_activity_path(@activity) 
    else 
     render 'edit' 
    end 
end 
... 

private 

    def activity_params 
     params.require(:activity).permit(:name, :active, #active is set to default: true 
             :timeslots_attributes => [:id, 
                    :time_start, 
                    :time_end, 
                    :day, 
                    :active]) 
    end 
end 

但每當我試圖創建一個新的活動，我得到錯誤信息「時隙活動必須存在」。

我覺得它試圖在活動創建之前分配activity_id時隙，但我不確定。我已經嘗試了很多東西（其中一些我已經在我的示例中添加了評論表單），但無法弄清楚爲什麼我會收到此錯誤。

更新：添加錯誤日誌

Started POST "/activities" for 127.0.0.1 at 2016-09-25 18:04:51 +0700 
Processing by ActivitiesController#create as HTML 
    Parameters: {"utf8"=>"✓", "authenticity_token"=>"xp+dBcWC4cjI6FLpIqhU0RzM4ldZ4JpkFLSyAXcmifL73QqWz6R65EHm/Tj7QxlXnWiBA0axjVXvMZHQ+XKA9A==", "activity"=>{"name"=>"Newest class", "timeslots_attributes"=>{"0"=>{"time_start(1i)"=>"2016", "time_start(2i)"=>"9", "time_start(3i)"=>"25", "time_start(4i)"=>"12", "time_start(5i)"=>"00", "time_end(1i)"=>"2016", "time_end(2i)"=>"9", "time_end(3i)"=>"25", "time_end(4i)"=>"13", "time_end(5i)"=>"30", "day"=>"4"}}}, "commit"=>"Create class"} 
    Club Load (0.2ms) SELECT "clubs".* FROM "clubs" WHERE "clubs"."id" = ? LIMIT ? [["id", 2], ["LIMIT", 1]] 
    (0.1ms) begin transaction 
    (0.1ms) rollback transaction 
    Rendering activities/new.html.erb within layouts/application 
    Rendered shared/_error_messages.html.erb (1.5ms) 
    Rendered activities/new.html.erb within layouts/application (16.9ms) 
    Rendered layouts/_rails_default.html.erb (58.5ms) 
    Rendered layouts/_shim.html.erb (0.5ms) 
    Rendered layouts/_header.html.erb (1.7ms) 
    Rendered layouts/_footer.html.erb (0.8ms) 
Completed 200 OK in 111ms (Views: 93.9ms | ActiveRecord: 0.3ms) 

Answer 1

由於Rails 5使belongs_to的默認屬性需要您收到此錯誤。此外，儲蓄機構種類如下：

validate your parent model 
validate your child model # validation fails here because parent doesn't have an id yet, because it hasn't been saved 
save parent model 
save child model 

一種方法來解決這個是：

class Activity < AR 
    has_many :timeslots, dependent: :destroy, inverse_of: :activity 
    accepts_nested_attributes_for :timeslots 
end 

class Timeslot < AR 
    belongs_to :activity, inverse_of: :timeslot 
end 

你可以瞭解更多的這here和here