为什么我无法获得 /comments/new.html.erb？

Question

我通过脚手架命令创建模型

class Post < ActiveRecord::Base
  has_many :comments, as: :commentable
end

class Comment < ActiveRecord::Base
  belongs_to :commentable , polymorphic: true
end

...

routes.rb:

 resources :posts, :images, :links do
    resources :comments
 end

cmets_controller.rb：

def new
  @comment = Comments.new
end

/posts/show.html.erb：

 <%= link_to 'Add comment', new_post_comment_path (@post)%>

这里我想我需要...(@post, @comment)，比如来自http://guides.rubyonrails.org/routing.html：

<%= link_to 'Ad details', magazine_ad_path(@magazine, @ad) %>

但我这里没有@comment。

我收到错误：

    Showing /home/loza/Projects/my_blog/app/views/comments/_form.html.erb where line #1 raised:

    undefined method `comments_path' for #<#<Class:0x007f2e4a77c2f0>:0x007f2e4ab23ef8>

Extracted source (around line #1): 
<%= form_for(@comment) do |f| %>
  <% if @comment.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@comment.errors.count, "error") %> prohibited this comment from being saved:</h2>

      <ul>

我需要怎么写才能得到/comments/new.html.erb？

今天我更正了我的代码： /posts/show.html.erb：

<%= link_to 'New comment', new_post_comment_path(@post, @post.comments.build) %>

/cmets_controller.rb:

  def new
    @post = Post.find(params[:post_id])
    @comment = @post.comments.new
  end

我又遇到了同样的错误：

Showing /home/loza/Projects/my_blog/app/views/comments/_form.html.erb where line #1 raised:

undefined method `comments_path' for #<#<Class:0x007fa736859320>:0x007fa73669e238>

xtracted source (around line #1):

  <%= form_for(@comment) do |f| %>
  <% if @comment.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@comment.errors.count, "error") %> prohibited this comment from being saved:</h2>

app/views/comments/_form.html.erb:1:in `_app_views_comments__form_html_erb___1254360398011104975_42800220'
app/views/comments/new.html.erb:3:in `_app_views_comments_new_html_erb__2117553728149416519_42948680'

问题出在哪里？我该如何解决？

Answer 1

正如错误所说，您遇到的错误位于 _cmets/form.html.erb：

form_for(@comment)

你需要@post 对象，form_for 才能找到正确的路径：

form_for([@post, @comment])

Answer 2

这是因为您不仅有 '/comments/new' 路径，而是 form_for(@comment) 正在尝试创建它。

您的路线正在创建类似'/post/:id/comments/new' 的路径，因此您必须使用form_for([@post, @comment])。

还可以在新方法中添加 @post = Post.find(params(:is)) 或更好地作为 before_action 回调。