调用错误方法时,"未定义的方法`错误'为nil:NilClass"

Question

我目前正在教自己一些RoR和教程,但添加一些更好的布局和引导程序的东西,我遇到了一个我无法弄清楚的问题.

我正在尝试进行验证部分(http://guides.rubyonrails.org/getting_started.html#adding-some-validation),但是当我使用时:

<% @post.errors.any? %>

我收到这条消息:

undefined method `errors' for nil:NilClass
Extracted source (around line #9):
<legend><h1>Add Post</h1></legend>

<%= form_for :post, url: posts_path, html: {class: 'form-horizontal'} do |f| %>
      <% if @post.errors.any? %>
        <div id="errorExplanation">

什么都行不通,我甚至复制并粘贴了教程中的部分.

以下是视图的代码:

<p> </p>

<div class="span6"

<fieldset>
    <legend><h1>Add Post</h1></legend>

    <%= form_for :post, url: posts_path, html: {class: 'form-horizontal'} do |f| %>
          <% if @post.errors.any? %>
            <div id="errorExplanation">

                <h2><%= pluralize(@post.errors.count, "error") %> prohibited this post from being saved:</h2>

                <ul>
                    <% @post.errors.full_messages.each do |msg| %>
                    <li><%= msg %></li>
                    <% end %>
                  </ul>
            </div>
  <% end %>
        <div class="control-group">
            <%= f.label :title, :class => 'control-label' %>
            <div class="controls">
                <%= f.text_field :title, :class => 'span4' %>
            </div>
        </div>

        <div class="control-group">
            <%= f.label :content, :class => 'control-label' %>
            <div class="controls">
                <%= f.text_area :content, :rows => '7', :class => 'input-block-level' %>
            </div>
        </div>

        <div class="form-actions">
            <%= f.submit "Add Post", :class => 'btn btn-success' %>
            <%= link_to "Cancel", posts_path, :class => 'btn', :style => 'float:right;' %>
        </div>
    <% end %>
</fieldset>

</div>

我的posts_controller:

class PostsController < ApplicationController

    def new
    end

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

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

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

    def index
        @posts = Post.order("created_at desc")
    end

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

end

我错过了什么？提前致谢!

Answer 1

您还需要@post在new动作中定义.

def new
  @post = Post.new
end

当你第一次在动作上加载表单时,你会收到NilClass错误,因为@post它没有值(它nil)new.

当你做render :new你的create行动那里,因为它的使用是没有问题的@post,你已经在顶部定义create.