9

我正在关注 Michael Hartl 的 Rails 指南(第 9 章)。当我尝试访问与用户个人资料对应的页面时,浏览器显示以下错误消息:

 NoMethodError in Users#show

Showing /home/jonathan/Desktop/railsTut/sample_app/app/views/users/show.html.erb where line #1 raised:

undefined method `name' for nil:NilClass

Extracted source (around line #1):

1: <% provide(:title, @user.name) %>
2: <div class="row">
3:   <aside class="span4">
4:     <section>

Rails.root: /home/jonathan/Desktop/railsTut/sample_app

这是我的 users_controller.rb

class UsersController < ApplicationController
  before_action :signed_in_user, only: [:edit, :update]

  def show
    @user = User.find(params[:id])
    end

  def new
    @user = User.new
  end

  def create
    @user = User.new(params[:user])    # Not the final implementation!
    if @user.save
     sign_in @user
     flash[:success] = "Welcome to the Sample App!"
     redirect_to @user
    else
      render 'new'
    end
  end

  def edit
    @user = User.find(params[:id])
  end

  def update
    @user = User.find(params[:id])
    if @user.update_attributes(params[:user])
         flash[:success] = "Profile updated"
         sign_in @user
         redirect_to @user
      else
           render 'edit'
      end
    end

  def destroy
 User.find(params[:id]).destroy
    flash[:success] = "User destroyed."
    redirect_to users_url
    end

private

  def user_params
    params.require(:user).permit(:name, :email, :password, :password_confirmation)
    end


  # Before filters

  def signed_in_user
    unless signed_in?
        store_location
        redirect_to signin_url, notice: "Please sign in."
    end
 end
end

页面加载良好,没有该行:

before_action :signed_in_user, only: [:edit, :update]

但是随着它的包含,事情会出错,我不知道为什么。

另外,这里是 routes.rb

SampleApp::Application.routes.draw do
  resources :users
  resources :sessions, only: [:new, :create, :destroy]

  root to: 'static_pages#home'

 match '/signup',  to: 'users#new'
  match '/signin',  to: 'sessions#new'
  match '/signout', to: 'sessions#destroy', via: :delete

  match '/help',    to: 'static_pages#help'
  match '/about',   to: 'static_pages#about'
  match '/contact', to: 'static_pages#contact'

end

任何帮助表示赞赏!

4

4 回答 4

19

如果确实 Hurman 的回答解决了您的问题,原因是您运行的是旧版本(即 <4.0.0)的 rails。before_filter在此版本中已重命名为before_actionhttps://github.com/rails/rails/commit/9d62e04838f01f5589fa50b0baa480d60c815e2c),Rails 4 中的更多信息: before_filter vs. before_action

于 2013-10-23T11:46:30.417 回答
16

而不是Users_controller中的Before Action尝试在过滤器之前所以您的代码如下所示:

before_filter :signed_in_user, only: [:edit, :update]

我有完全相同的错误!

于 2013-09-14T15:42:14.950 回答
2

我在使用4.1.6时遇到了同样的问题。问题是您已将 before_action 定义为private,我不知道为什么,但这种可见性与控制器在 Rails 中的 before_action 负载相混淆。因此,只需将其带到signed_in_user该区域之外,它就会重新开始工作。

希望这可以帮助!

于 2014-10-12T12:00:30.640 回答
1

继@Hurman Gul 的回答之后,我希望能给你一些关于你为什么会看到这个问题的细节......


您的控制器正在对不存在的变量执行操作

您遇到的错误是因为您的操作之一是尝试对未设置或没有内容(为nil)的变量执行操作。该错误基本上意味着您正在尝试调用不存在的变量的“.name”部分

undefined method `name' for nil:NilClass

Extracted source (around line #1):

1: <% provide(:title, @user.name) %>
2: <div class="row">
3:   <aside class="span4">
4:     <section>

Rails.root: /home/jonathan/Desktop/railsTut/sample_app

这基本上意味着在您看来,您正在尝试加载@user.name,而@user 可能不存在。我建议解决此问题的方法是最初将一些逻辑应用于您的视图:

#app/views/users/show.html.erb
<% unless defined?(@user) %>
    Sorry, we could not find your user!
<% else %>

 your code

<% end %>
于 2013-10-23T12:21:34.407 回答