"未定义的方法`标题'为nil:NilClass"Rails指南教程

Question

我正在研究RailsGuides教程(创建一个博客应用程序).当我运行服务器并打开时:/posts/new一切看起来都很好.但是,当我尝试创建帖子时,我收到此错误:

帖子#show中的NoMethodError

显示/home/darek/rails_projects/blog/app/views/posts/show.html.erb在行#3提出:

nil的未定义方法`title':NilClass

提取的来源(第3行):

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特定帖子时,我收到此错误.我的第一个线索就是换线

<%= @post.title %> 

至

<%= @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,我获得了标题,而文本形式为空.这不是我想要看到的;)

好的,这是代码

Show.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

耙路:

-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

你已经使你的方法变得私密.记住你把private关键字放在哪里.下面的所有方法将变为私有,定义你的方法.控制器末尾的私有方法:

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

Answer 2

在学习本教程时,我遇到了同样的问题.我再次检查了我的代码然后找到了原因.在posts_controller.rb文件中,您不能将私有方法放在代码中间,这意味着下面的所有方法(例如show,edit)都将是私有的.相反,将私有方法放在底部,如下所示:

class PostsController < ApplicationController
    def new
    end
    def index
        @posts = Post.all
    end
    def create
        @post = Post.new(post_params)
        @post.save
        redirect_to @post
    end
    def show
        @post = Post.find(params[:id])
    end
    private
        def post_params
            params.require(:post).permit(:title, :text)
        end
end

希望能解决你的问题.