Rails指南「未定義的方法'評論'爲零：NilClass」

Question

我是Rails的新手，並且通過Getting Started Guide工作。我通過this閱讀了關於該指南的類似問題，但看起來並不相關。

我被困在第6.3節，我們試圖讓用戶在博客文章中添加評論。我已經在帖子顯示視圖中添加了一個評論表單，該表單之前工作正常，但現在引發了以下錯誤。什麼是問題？

NoMethodError in Posts#show 

Showing /Users/.../Desktop/Rails Blog/blog/app/views/posts/show.html.erb where line #24 raised: 

undefined method `comments' for nil:NilClass 



Extracted source (around line #24): 

    21 <% end %> 
    22 
    23 <h2>Add a comment:</h2> 
    24 <%= form_for([@post, @posts.comments.build]) do |f| %> 
    25 <p> 
    26   <%= f.label :commenter %><br /> 
    27   <%= f.text_field :commenter %> 

posts_controller.rb：

class PostsController < ApplicationController 
    def index 
     @posts = Post.all 
    end 
    def new 
     @post = Post.new 
    end 
    def create 
     @post = Post.new(params[:post].permit(:title, :text)) 
     if @post.save 
      redirect_to @post 
     else 
      render 'new' 
     end 
    end 
    def edit 
     @post = Post.find(params[:id]) 
    end 
    def update 
     @post = Post.find(params[:id]) 

     if @post.update(params[:post].permit(:title, :text)) 
      redirect_to @post 
     else 
      render 'edit' 
     end 
    end 
    def show 
     @post = Post.find(params[:id]) 
    end 
    def destroy 
     @post = Post.find(params[:id]) 
     @post.destroy 
     redirect_to posts_path 
    end 
    private 
     def post_params 
      params.require(:post).permit(:title, :text) 
     end 
end 

comments_controller：

class CommentsController < ApplicationController 
    def create 
     @post = Post.find(params[:post_id]) 
     @comment = @post.comments.create(params[:comment].permit(:commenter, :body)) 
     redirect_to post 
    end 
end 

posts.show.html.erb：

<p> 
    <strong>Title:</strong> 
    <%= @post.title %> 
</p> 

<p> 
    <strong>Text:</strong> 
    <%= @post.text %> 
</p> 

<h2>Comments</h2> 
<% @post.comments.each do |comment| %> 
    <p> 
     <strong>Commenter:</strong> 
     <%= comment.commenter %> 
    </p> 
    <p> 
     <strong>Comment:</strong> 
     <%= comment.body %> 
    </p> 
<% end %> 

<h2>Add a comment:</h2> 
<%= form_for([@post, @posts.comments.build]) do |f| %> 
    <p> 
     <%= f.label :commenter %><br /> 
     <%= f.text_field :commenter %> 
    </p> 
    <p> 
     <%= f.label :body %><br /> 
     <%= f.text_area :body %> 
    </p> 
    <p> 
     <%= f.submit %> 
    </p> 
<% end %> 

<%= link_to 'Back', posts_path %> 
<%= link_to 'Edit', edit_post_path(@post) %> 

Answer 1

您有@posts。該變量被稱爲@post。放下「s」。