ruby-on-rails - Rails 关联 new_path 错误

Question

我的 Rails 应用程序中有两个模型帖子和主题

class Post < ActiveRecord::Base
  #relation between topics and post
  belongs_to :topic

  #post is valid only if it's associated with a topic:

   validates :topic_id, :presence => true
  #can also require that the referenced topic itself be valid
  #in order for the post to be valid:

  validates_associated :topic



end

和

class Topic < ActiveRecord::Base
  #relation between topics and post
  has_many :posts
end

我正在尝试在它们之间建立关联。

我想要每个主题对应的多篇帖子

我使用了嵌套路由

Rails.application.routes.draw do


  # nested routes
  resources :topics do
    resources :posts
  end

      resources :userdetails


  devise_for :users, :controllers => { :registrations => "registrations" }

我的 Post Controller 看起来像

class PostsController < ApplicationController
 # before_action :set_post, only: [:show, :edit, :update, :destroy]

  before_filter :has_userdetail_and_topic, :only =>[:new, :create]



  # GET /posts
  # GET /posts.json

  #for new association SAAS book

  protected
  def has_userdetail_and_topic

    unless(@topic =Topic.find_by_id(params[:topic_id]))
      flash[:warning] = 'post must be for an existing topic'
    end
  end

  public

  def new
    @post = @topic.posts.build
    #@@topic = Topic.find(params[:topic_id1])

  end

  def index
    @posts = Post.all
  end

  # GET /posts/1
  # GET /posts/1.json
  def show
  end

  # GET /posts/new


  # GET /posts/1/edit
  def edit
  end

  # POST /posts
  # POST /posts.json
  def create



    #@topic.posts << @post
    #@current_user = current_user.id
    @current_user.posts << @topic.posts.build(params[:post])
    #@post = Post.new(post_params )

    #@post.userdetail_id = current_user.id

     #Association functional between topic and post
     #Class variable used
     #@@topic.posts << @post

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

  # PATCH/PUT /posts/1
  # PATCH/PUT /posts/1.json
  def update
    respond_to do |format|
      if @post.update(post_params)
        format.html { redirect_to @post, notice: 'Post was successfully updated.' }
        format.json { render :show, status: :ok, location: @post }
      else
        format.html { render :edit }
        format.json { render json: @post.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /posts/1
  # DELETE /posts/1.json
  def destroy
    @post.destroy
    respond_to do |format|
      format.html { redirect_to posts_url, notice: 'Post was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def post_params
      params.require(:post).permit(:topic_id,:issue, :description, :rating, :userdetail_id)
    end
end

我正在尝试通过代码 <td><%= link_to 'Write', new_topic_post_path(@topic) %> </td> 从主题/索引导航

但是当我尝试访问localhost:3000/topics]时 我收到错误

No route matches {:action=>"new", :controller=>"posts", :topic_id=>nil} missing required keys: [:topic_id]

任何人都可以告诉我这个错误吗，因为我是 Rails 新手，请明确指定答案。 我还有一个疑问，请告诉我是否错误地关联了主题和帖子。我对这行代码感到困惑 -

@topic.posts << @post 

Answer 1

错误缺少必需的键:[:topic_id]告诉您的是，您需要提供带有键topic_id的哈希:

<%= link_to 'Write', new_topic_post_path(topic_id: @topic) %>

将资源传递给路由助手仅适用于 id 参数:

<%= link_to @topic, topic_path(@topic) %>

是一种简写形式:

<%= link_to @topic, topic_path(id: @topic.to_param) %>

添加:

@prcu 也是正确的。 @topic 记录需要保存到数据库中。未保存的记录没有 id，因为数据库在插入记录时分配 id 列。

您还需要在 PostsController 中设置 @topic 实例变量:

@topic = Topic.find(params[:id])

这通常是通过 before 过滤器完成的:

before_filter :set_topic, only: [:new]  

def set_topic
   @topic = Topic.find(params[:id])
end

同样的事情也需要在TopicsController#index中完成。