未定義的局部變量或方法'後」

Question

這裏是我的我的意見_form.html.erb形式：

<%= form_for([post, @comment]) do |f| %> 
    <p> 
     <%= f.text_area :body, placeholder: "Write a comment!" %> 
    </p> 
    <br> 
    <p> <%= f.submit %> </p> 

<% end %> 

，這裏是我的職位形成_form.html.erb：

<%= form_for @post, url: post_path(@post), method: :patch do |f| %> 
     <% if @post.errors.any? %> 
      <div id="errors"> 
      <h2><%= pluralize(@post.errors.count, "Error") %> Prevent this post from posting</h2> 
      <ul> 
       <% @post.errors.full_messages.each do |msg| %> 
        <li><%= msg %></li> 

       <% end %> 
      </ul> 
      </div> 
     <% end %> 
     <p> 
      <%= f.label :Edit_Post %><br> 
      <%= f.text_area :body %> 
     </p> 
     <p> 
      <%= f.submit %> 
     </p> 

<% end %> 

這裏是我的comments_controller.rb：

class CommentsController < ApplicationController 
    def create 
     @post = Post.find(params[:post_id]) 
     @comment = @post.comments.build(params[:comment]) 
     @comment.save 
     redirect_to @posts 
    end 
    def destroy 
     @user = User.find(session[:user_id]) 
     @posts = Post.find(params[:post_id]) 
     @comment = @post.comments.find(params[:id]) 
     @comment.destroy 
     redirect_to post_path(@post) 
    end 
end 

這裏是我的posts_controller.rb：

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

    def index 
     @user = User.find(session[:user_id]) 
     @posts = Post.all 
    end 
    def welcome 
     @user = User.find(session[:user_id]) 
     @posts = Post.order("created_at desc").limit(4).offset(1) 
     @signed_in_user = session[:user_id] 
    end 
    def posts 
     @user = User.find(session[:user_id]) unless session[:user_id] == nil 
     redirect_to login_path, notice: "You're not logged in" unless @user 
     @signed_in_user = session[:user_id] 

    end 
    def new 
     @post = Post.new 
     @user = User.find(session[:user_id]) 
    end 
    def create 
     @user = User.find(session[:user_id])   
     @post = Post.new(post_params) 

     @post.user_id = @signed_in_user 

     if @post.save 
      redirect_to dashboard_path 
     else 
      render 'new' 
     end 
    end 
    def show 
     @user = User.find(session[:user_id]) 

     @signed_in_user = session[:user_id] 
    end 
    def edit 
     @user = User.find(session[:user_id]) 
    end 

    def update 
     if @post.update(post_params) 
      redirect_to @post, notice: "Your post has been updated!" 
     end 
    end 
    def destroy 
     @user = User.find(session[:user_id]) 
     @post.user_id = @signed_in_user 

     @post.destroy 

     redirect_to posts_path 
    end 

    private 

    def load_post 
     @post = Post.find(params[:id]) 
    end 
    def post_params 
     params.require(:post).permit(:body) 
    end 
end 

有此問題。任何幫助將不勝感激。這裏是我有錯誤的圖片：

編輯：這是我的日誌

Started GET "/posts/24" for 127.0.0.1 at 2015-09-28 18:46:44 -0700 
Processing by PostsController#show as HTML 
    Parameters: {"id"=>"24"} 
    [1m[36mPost Load (0.0ms)[0m [1mSELECT "posts".* FROM "posts" WHERE "posts"."id" = ? LIMIT 1[0m [["id", 24]] 
    [1m[35mUser Load (0.0ms)[0m SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 1]] 
    [1m[36mCACHE (0.0ms)[0m [1mSELECT "posts".* FROM "posts" WHERE "posts"."id" = ? LIMIT 1[0m [["id", "24"]] 
    [1m[35m (0.0ms)[0m SELECT COUNT(*) FROM "comments" WHERE "comments"."post_id" = ? [["post_id", 24]] 
    Rendered comments/_form.html.erb (1.0ms) 
    Rendered posts/show.html.erb within layouts/application (7.0ms) 
    Rendered layouts/_nav.html.erb (1.0ms) 
Completed 200 OK in 451ms (Views: 412.0ms | ActiveRecord: 1.0ms) 

Answer 1

undefined local variable or method `post' 

你的錯誤消息說明了一切。它告訴你，你的視圖沒有在相應的控制器動作中定義post。這就是爲什麼你得到這個錯誤。

因此，您需要在相應的控制器操作中定義@post（通常您在此類情況下使用實例變量），即PostsController的show操作。您實際上需要定義@comment以及當前您的控制器操作中沒有它。因此，更新show方法是這樣的：

def show 
    @user = User.find(session[:user_id]) 
    @signed_in_user = session[:user_id] 

    # you need to define @post and @comment 
    @post = Post.find params[:id] 
    @comment = Comment.new(post: @post) 
end 

然後，您可以在視圖中使用@post和@comment，所以你comments/_form.html.erb應該是這樣的：

<%= form_for([@post, @comment]) do |f| %> 
. . . 
. . . 

Answer 2

Rails可以從控制器通過實例變量的觀點，你應該使用@post在更換postconmments/_form.html.erb。

<%= form_for([@post, @comment = @post.comments.build]) do |f| %>