用户#index 中的 NoMethodError ||数据库问题

Question

我是 RoR 的新手。我一直在学习一个教程，我必须生成脚手架用户 first_name last_name 然后迁移到数据库。出于某种原因，当我尝试推送到 Git 中的新分支时，一些更改丢失了。然后我无法加载本地服务器，出现与数据库相关的错误。经过长时间试图找出问题所在，我放弃了，决定销毁并重新迁移数据库。

我尝试生成脚手架用户 first_name last_name，但控制台给我一个错误：

The name 'User' is either already used in your application or reserved by Ruby on Rails. Please choose an alternative and run this generator again.

虽然索引页面看起来不错，并且我可以创建用户并正常登录/注销，但当我尝试访问 http://localhost:3000/users/ 时，我收到此错误：

NoMethodError in Users#index
Showing /Users/Jen/nameofapp/app/views/users/index.html.erb where line #16 raised:

undefined method `first_name' for # User:0x007febdf5938a0

这些是我的代码 sn-ps：

视图/用户/index.html.erb

    <p id="notice"><%= notice %></p>

<h1>Listing Users</h1>
  <table>
    <thead>
      <tr>
        <th>First name</th>
        <th>Last name</th>
        <th colspan="3"></th>
      </tr>
    </thead>

    <tbody>
      <% @users.each do |user| %>
        <tr>
          <td><%= user.first_name %></td>
          <td><%= user.last_name %></td>
          <td><%= link_to 'Show', user , class:"btn btn-default btn-xs" %></td>
          <td><%= link_to ('<span class="glyphicon glyphicon-pencil"></span>').html_safe, edit_user_path(user) %></td>
          <td><%= link_to ('<span class="glyphicon glyphicon-remove"></span>').html_safe, user, method: :delete, data: { confirm: 'Are you sure?' } %></td>
        </tr>
      <% end %>
    </tbody>
  </table>
<br>

<div class="col-sm-6 col-md-4">
  <%= link_to 'New User', new_user_path, class:"btn btn-default btn-xs" %>
</div>

models/user.rb

    class User < ApplicationRecord

      devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

      has_many :orders     
    end

控制器/users_controller.rb

class UsersController < ApplicationController
  before_filter :authenticate_user!, :except => [:show, :index]
  before_action :set_user, only: [:show, :edit, :update, :destroy]
  load_and_authorize_resource

  # GET /users
  # GET /users.json
  def index
    @users = User.all
  end

  # GET /users/1
  # GET /users/1.json
  def show
  end

  # GET /users/new
  def new
    @user = User.new
  end

  # GET /users/1/edit
  def edit
  end

  # POST /users
  # POST /users.json
  def create
    @user = User.new(user_params)

    respond_to do |format|
      if @user.save
        format.html { redirect_to @user, notice: 'User was successfully created.' }
        format.json { render :show, status: :created, location: @user }
      else
        format.html { render :new }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /users/1
  # PATCH/PUT /users/1.json
  def update
    respond_to do |format|
      if @user.update(user_params)
        format.html { redirect_to @user, notice: 'User was successfully updated.' }
        format.json { render :show, status: :ok, location: @user }
      else
        format.html { render :edit }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /users/1
  # DELETE /users/1.json
  def destroy
    @user.destroy
    respond_to do |format|
      format.html { redirect_to users_url, notice: 'User was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_user
      @user = User.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def user_params
      params.require(:user).permit(:first_name, :last_name)
    end
end

Answer 1

如果您已经将Devise 用于User 类，则可以使用scaffold。但是，您可以创建另一个迁移文件以将这些列添加到 users 表中

rails g migration AddFieldsToUser

然后里面迁移

def change
  add_column :users, :first_name, :string
  add_column :users, :last_name, :string
end

由于你是新手，我正在编写这些代码 sn-ps。