NoMethodError使用Rails 4.0和嵌套形式茧

Question

我正在学习用Rails 4.0和我使用Cocoon创建一个简单的投票程序的嵌套形式。

用户应该能够添加一个新的问题，然后添加尽可能多的答案，因为他们想。

我有工作的嵌套形式，但是当我试图挽救该调查，我收到说NoMethodError in PollsController#create - undefined method ``answer' for #<Poll:0x007fba59a70dd0>

错误下面是从我Polls_Controller的相关信息：

before_action :set_poll, only: [:show, :edit, :update, :destroy] 

def create 
    @poll = Poll.new(poll_params) 

    respond_to do |format| 
     if @poll.save 
     format.html { redirect_to @poll, notice: 'Poll was successfully created.' } 
     format.json { render :show, status: :created, location: @poll } 
     else 
     format.html { render :new } 
     format.json { render json: @poll.errors, status: :unprocessable_entity } 
     end 
    end 
    end 

private 
def poll_params 
    params.require(:poll).permit(:question, :expires, answers_attributes: [:id, :answer, :_destroy]) 
end 

投票型号

class Poll < ActiveRecord::Base 
    has_many :answers, :class_name => "Answer" 

    accepts_nested_attributes_for :answers, reject_if: :all_blank, allow_destroy: true 

    validates :answer, presence: true 
end 

答案和模型

class Answer < ActiveRecord::Base 
    belongs_to :poll 
end 

下面是包含轮询形式和应答（嵌套的）形式在两个.erb谐音。

_form.html.erb

<%= form_for(@poll) do |f| %> 
    <% if @poll.errors.any? %> 
    <div id="error_explanation"> 
     <h2><%= pluralize(@poll.errors.count, "error") %> prohibited this poll from being saved:</h2> 

     <ul> 
     <% @poll.errors.full_messages.each do |message| %> 
     <li><%= message %></li> 
     <% end %> 
     </ul> 
    </div> 
    <% end %> 

    <div class="form-group"> 
    <%= f.label :question %><br> 
    <%= f.text_field :question, class: "form-control" %> 
    </div> 

    <div class="form-group" id="answers"> 
     <%= f.fields_for :answers do |answer| %> 
     <%= render 'answer_fields', f: answer %> 
     <% end %> 
     <div class="links"> 
      <%= link_to_add_association 'Add Answer', f, :answers, class: "btn btn-default add-button" %> 
     </div> 

    </div> 

    <div class="form-group"> 
     <%= f.label :expires %><br> 
     <%= f.datetime_select :expires %> 
    </div> 

    <div class="actions"> 
    <%= f.submit %> 
    </div> 
<% end %> 

_answer.html.erb

<div class="nested-fields form-group"> 
     <div class="field"> 
    <%= f.label :answer %> 
    <br/> 
    <%= f.text_field :answer, class: "form-control" %> 
    </div> 
    <%= link_to_remove_association "remove answer", f, class: "form-button btn btn-default" %> 
</div> 

我在这个一直盯着太久尽管它是一个简单的想法，我的大脑ISN没有看到这个问题。有任何想法吗？

编辑这里是我的架构

ActiveRecord::Schema.define(version: 20151104213600) do 

    create_table "answers", force: :cascade do |t| 
    t.text  "answer" 
    t.integer "poll_id" 
    t.datetime "created_at", null: false 
    t.datetime "updated_at", null: false 
    end 

    add_index "answers", ["poll_id"], name: "index_answers_on_poll_id" 

    create_table "polls", force: :cascade do |t| 
    t.string "question" 
    t.datetime "expires" 
    t.datetime "created_at", null: false 
    t.datetime "updated_at", null: false 
    end 

end 

Answer 1

我已经遇到这个问题我自己，并通过预先建立关联关系，它的工作就像一个魅力，这样做：

def new 
    @poll = Poll.new 
    @poll.answers.build 
end