嵌套对象不会保存[Rails 4]

Question

我正在使用Rails构建一个论坛。

当您创建主题时，它将具有Topic类中的Name和Description以及Post类中的Post内容...（当您创建一个线程时，您将自动创建一个包含内容的帖子）

含义： 对于每个主题，您可以有多个帖子 对于每个帖子，您必须有一个主题。

由于某些原因，当我创建主题时，它会保存主题的输入，但会抛出Post类的输入。

我环顾了整个Stackoverflow，发现了一些类似的问题，并尝试了很多答案，只是为了得到错误或没有任何改变。 （accepts_nested_attributes_for not saving the child attribute to the database，

模型

class Topic < ActiveRecord::Base 
    belongs_to :forum 
    has_many :posts, :dependent => :destroy 
    belongs_to :user 

    accepts_nested_attributes_for :posts 
end 

class Post < ActiveRecord::Base 
    belongs_to :topic 
end 

控制器 - 主题

class TopicsController < ApplicationController 
    before_action :set_topic, only: [:show, :edit, :update, :destroy] 

    def index 
    @topics = Topic.all 
    end 

    def new 
    @topic = Topic.new 
    responses = @topic.posts.build 
    end 

    def create 
    @topic = Topic.new(topic_params) 

    if @topic.save 
     flash[:success] = "Topic Posted" 
     redirect_to "/forums/#{@topic.forum_id}" 
    else 
     render :new 
    end 
    end 


    private 
    # Use callbacks to share common setup or constraints between actions. 
    def set_topic 
     @topic = Topic.find(params[:id]) 
    end 

    # Never trust parameters from the scary internet, only allow the white list through. 
    def topic_params 
     params.require(:topic).permit(:name, :description, :last_poster_id, :last_post_at, :forum_id, 
     posts_attributes: [:id, :content]) 
    end 
end 

_form

<%= form_for(@topic) do |f| %> 
    <% if params[:forum] %> 
    <input type="hidden" 
    id="topic_forum_id" 
    name="topic[forum_id]" 
    value="<%= params[:forum] %>" /> 
    <% end %> 

    <div class="field"> 
    <%= f.label :name %><br> 
    <%= f.text_field :name %> 
    </div> 
    <div class="field"> 
    <%= f.label :description %><br> 
    <%= f.text_field :description %> 
    </div> 

    <%= f.fields_for :responses do |p| %> 

    <%= p.label :content %><br /> 
    <%= p.text_area :content %> 

    <% end %> 


    <%= f.submit :class => "btn btn-primary" %> 
<% end %> 

Answer 1

感谢davidfurber，我弄清楚了什么是错的。如果其他人有同样的问题，这是解决方案。

您不需要将@ topic.posts.build分配给变量。这就是说，你不需要_form视图中的响应。相反，把：帖子：答复是。

_form

<%= form_for(@topic) do |f| %> 
    ... 
    <div class="field"> 
    <%= f.label :description %><br> 
    <%= f.text_field :description %> 
    </div> 

    <%= f.fields_for :posts do |p| %> 
    <%= p.label :content %><br /> 
    <%= p.text_area :content %> 
    <% end %> 

    <%= f.submit :class => "btn btn-primary" %> 
<% end %> 

控制器 - 主题

class TopicsController < ApplicationController 
    before_action :set_topic, only: [:show, :edit, :update, :destroy] 
    def new 
    @topic = Topic.new 
    @topic.posts.build 
    end 

    def create 
    # render text: topic_params and return 
    @topic = Topic.new(topic_params) 

    if @topic.save 
     flash[:success] = "Topic Posted" 
     redirect_to "/forums/#{@topic.forum_id}" 
    else 
     render :new 
    end 
    end 

    private 
    # Use callbacks to share common setup or constraints between actions. 
    def set_topic 
     @topic = Topic.find(params[:id]) 
    end 

    # Never trust parameters from the scary internet, only allow the white list through. 
    def topic_params 
     params.require(:topic).permit(:name, :description, :last_poster_id, :last_post_at, :forum_id, 
     posts_attributes: [:id, :content]) 
    end 
end