ruby-on-rails - "undefined method ` 标题 ' for nil:NilClass"Rails 指南教程

Question

我正在编写 RailsGuides 教程(创建博客应用程序)。当我运行服务器并打开:/posts/new一切看起来都很好。但是，当我尝试创建帖子时，出现此错误:

NoMethodError in Posts#show

Showing /home/darek/rails_projects/blog/app/views/posts/show.html.erb where line #3 raised:

undefined method `title' for nil:NilClass

提取的源代码(在第 3 行附近):

1  <p>
2  <strong>Title:</strong>
3  <%= @post.title %>
4  </p>
5  <p>

事实上 post 已创建，我可以在/posts 看到标题和内容
但是当我尝试使用 show specific post 时，我得到了这个错误。
我的第一个线索是换线

<%= @post.title %> 

到

<%= @post.try(:title) %>

错误消失了，但问题没有解决。
当我尝试显示特定帖子时，我得到标题，而文本表单为空。这不是我想看到的；)

好的，这是代码

显示.html.erb

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

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


<h2>Add a comment:</h2>
<%= form_for([@post, @post.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 'Edit Post', edit_post_path(@post) %> |
<%= link_to 'Back to Posts', posts_path %>

Posts_controller.rb

class PostsController < ApplicationController

  def new 
    @post = Post.new
  end

  def index
    @posts = Post.all
  end

  def create
  @post = Post.new(params[:post].permit(:title, :text))

  if @post.save
  redirect_to @post
  else
    render 'new'
  end
end

private
  def post_params
   params.require(:post).permit(:title, :text)
  end

   def show
      @post = Post.find(params[:id])
   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 destroy
      @post = Post.find(params[:id])
      @post.destroy

      redirect_to posts_path
    end
end

rake 路线:

-VirtualBox:~/rails_projects/blog$ rake routes
           Prefix Verb   URI Pattern                                 Controller#Action
    post_comments GET    /posts/:post_id/comments(.:format)          comments#index
                  POST   /posts/:post_id/comments(.:format)          comments#create
 new_post_comment GET    /posts/:post_id/comments/new(.:format)      comments#new
edit_post_comment GET    /posts/:post_id/comments/:id/edit(.:format) comments#edit
     post_comment GET    /posts/:post_id/comments/:id(.:format)      comments#show
                  PATCH  /posts/:post_id/comments/:id(.:format)      comments#update
                  PUT    /posts/:post_id/comments/:id(.:format)      comments#update
                  DELETE /posts/:post_id/comments/:id(.:format)      comments#destroy
            posts GET    /posts(.:format)                            posts#index
                  POST   /posts(.:format)                            posts#create
         new_post GET    /posts/new(.:format)                        posts#new
        edit_post GET    /posts/:id/edit(.:format)                   posts#edit
             post GET    /posts/:id(.:format)                        posts#show
                  PATCH  /posts/:id(.:format)                        posts#update
                  PUT    /posts/:id(.:format)                        posts#update
                  DELETE /posts/:id(.:format)                        posts#destroy
             root GET    /                                           welcome#index
                  GET    /posts/:id(.:format)                        posts#view
                  DELETE /posts/:id(.:format)                        posts#destroy

感谢您的帮助和兴趣!

Answer 1

您已将方法设为私有(private)。记住你把私有(private)关键字放在哪里。下面的所有方法都将变成私有(private)的，像这样定义你的方法。 Controller 末尾的私有(private)方法:

class PostsController < ApplicationController

def new 
  @post = Post.new
end

def index
  @posts = Post.all
end

def create
@post = Post.new(params[:post].permit(:title, :text))

  if @post.save
    redirect_to @post
  else
    render 'new'
  end
end

def show
  @post = Post.find(params[:id])
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 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

希望它会有所帮助。谢谢