为什么在控制器的方法中定义的实例变量在相应的部分中不可用? [英] Why aren't instance variables defined in a controller's methods available in the corresponding partials?

问题描述

例如，给定一个基本的控制器，例如:

class PostsController <应用控制器定义索引@post = Post.all结尾

实例变量 @post 在视图 posts/index.html.erb 中可用，但在部分 posts/_index.html.erb 中不可用代码>

我的主要问题是:这是为什么?以及如何为控制器中的部分定义方法，例如传递实例变量?

更具体的说明:我问这个是因为我在一个单独的主视图中呈现数据的方式 welcome/index.html.erb 是通过这个帖子部分的.我通过在 posts/_index.html.erb 部分中使用 Post.all 直接调用模型来绕过这个限制，但据我所知，这忽略了 MVC 架构并且严重限制了我开发更复杂的方法，除非我真的打破惯例并将它们写入视图(我认为这可能有效但设计不佳).

目前，@post 正在向部分符号 :post 传递一个 nil 到welcome/index.html.erb

显然我遗漏了一些东西，所以任何见解将不胜感激！

谢谢

相关文件:

views/帖子/_index.html.erb_new.html.erb显示.html.erb欢迎/index.html.erb控制器/post_controller.rbWelcome_controller.rb

posts/_index.html.erb

<% post.reverse.each do |post|％＞<div class="panel panel-default"><div class="panel-body"><%= post.text %>

<%结束%>

posts/_new.html.erb

<%= form_for :post, url: posts_path do |f|％＞<p id="post_box"><%= f.text_area :text %></p><p><%= f.submit %></p><%结束%>

posts/show.html.erb

<%= @post.text %>

welcome/index.html.erb 相关部分(部分)

<%= render partial: "posts/index", locals: {post: @post} %><%= 渲染部分:"posts/new" %>

controllers/posts_controller.rb

class PostsController <应用控制器定义新结尾定义创建@post = Post.new(post_params)@post.save重定向到/"结尾高清秀@post = Post.find(params[:id])结尾定义索引@post = Post.all结尾私人的def post_paramsparams.require(:post).permit(:text)结尾结尾

控制器/welcome_controller.rb

class WelcomeController <应用控制器结尾

解决方案

您是对的，您在视图中调用控制器级对象查找违反了 MVC 约定.

当您对部分调用渲染操作时，您需要发送各种参数，其中之一是 locals 哈希，它采用您想直接传递到部分的变量.

看起来像这样:

<%= render partial: "something", locals: {posts: @posts} %>

Rails 指南是有关该主题的重要资源.在此处了解更多相关信息.

For example, given a basic controller such as:

class PostsController < ApplicationController
  def index
    @post = Post.all
  end

The instance variable @post is available in the view posts/index.html.erb but not the partial posts/_index.html.erb

My primary questions are: Why is this? and How can I define a method for a partial in a controller to for example, pass an instance variable?

On a more specific note: I ask this because the way I am rendering data in a separate, primary view welcome/index.html.erb is via this posts partial. I have gotten around this limitation by directly calling the model with Post.all in the posts/_index.html.erb partial, but as far as I understand this ignores MVC architecture and severely limits me from developing more complex methods, unless I really break convention and write them into the view (which I assume may work but is poor design).

Currently, @post is passing a nil to the partial symbol :post in welcome/index.html.erb

Clearly I'm missing something, so any insight would be greatly appreciated!

Thank you

Relevant files:

views/
  posts/
    _index.html.erb
    _new.html.erb
    show.html.erb
  welcome/
    index.html.erb

controllers/ 
  posts_controller.rb
  welcome_controller.rb

posts/_index.html.erb

<% post.reverse.each do |post| %>
  <div class="panel panel-default">
    <div class="panel-body">
      <%= post.text %>
    </div>
  </div>
<% end %>

posts/_new.html.erb

<%= form_for :post, url: posts_path do |f| %>
  <p id="post_box">
    <%= f.text_area :text %>
  </p>

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

posts/show.html.erb

<%= @post.text %>

welcome/index.html.erb relevant portions (partials)

<%= render partial: "posts/index", locals: {post: @post} %>
<%= render partial: "posts/new" %>

controllers/posts_controller.rb

class PostsController < ApplicationController
  def new
  end

  def create
    @post = Post.new(post_params)

    @post.save
    redirect_to '/'
  end

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

  def index
    @post = Post.all
  end

  private
    def post_params
      params.require(:post).permit(:text)
    end

end

controllers/welcome_controller.rb

class WelcomeController < ApplicationController
end

解决方案

You're right that you're breaking MVC conventions by calling controller-level object lookups in your view.

When you call the render action on the partial you have a variety of arguments to send, one of which is a locals hash that takes a variable you want to pass directly into your partial.

It looks like this:

<%= render partial: "something", locals: {posts: @posts} %>

The rails guides are a great resource on the topic. More on that here.

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