ruby-on-rails - 未定义方法 `errors' 为 nil :NilClass in app/views/articles/new. html.erb

Question

我正在关注 http://guides.rubyonrails.org/getting_started.html并尝试向文本字段添加验证。我的类(class):

class Article < ActiveRecord::Base

    validates :title, presence: true, length: { minimum: 5 }

    def new
      @article = Article.new
    end

    def create
    @article = Article.new(article_params)

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

    private
    def article_params
        params.require(:article).permit(:title, :text)
    end

end

我的 new.html.erb 文件:

<%= form_for :article, url: articles_path do |f| %>

  <% if @article.errors.any? %>
    <div id="error_explanation">
      <h2>
        <%= pluralize(@article.errors.count, "error") %> prohibited
        this article from being saved:
      </h2>
      <ul>
        <% @article.errors.full_messages.each do |msg| %>
          <li><%= msg %></li>
        <% end %>
      </ul>
    </div>
  <% end %>

  <p>
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </p>

  <p>
    <%= f.label :text %><br>
    <%= f.text_area :text %>
  </p>

  <p>
    <%= f.submit %>
  </p>

<% end %>

当我尝试添加新文章时，我打开了 http://localhost:3000/articles/new但我看到的不是表格，而是错误 undefined method errors' for nil:NilClass因为这行错误 <% if @article.errors.any? %>

我在这里错过了什么。看起来像 @article在创建之前是否正在验证？我该如何解决？

Answer 1

您的模型和 Controller 都啮合在一起成为一个类。那行不通。

你需要两个类:

• 一个名为 Article 的模型继承自 ActiveRecord::Base
• 一个名为 ArticlesController 的 Controller 继承自 ApplicationController

您发布的代码是模型，但您添加的操作(new 和 create)需要进入 Controller 。

您所遵循的指南说(注意文件名):

Rails includes methods to help you validate the data that you send to models. Open the app/models/article.rb file and edit it:

class Article < ActiveRecord::Base
    validates :title, presence: true,
             length: { minimum: 5 }
end

下面是

... to do this, change the new and create actions inside app/controllers/articles_controller.rb to these:

def new
  @article = Article.new
end

def create
  @article = Article.new(article_params)

  # ...