使用 :alert（或 :notice）和 render 方法，来自 Ruby On Rails 指南“Layouts and Rendering in Rails”，对我不起作用：

The use of :alert (or :notice) with the render method, from the Ruby On Rails guide called 'Layouts and Rendering in Rails', does not work for me:

提问by Caroline Schnapp

The use of :alert (or :notice) with the render method, from the Ruby On Rails guide called 'Layouts and Rendering in Rails' at http://guides.rubyonrails.org/layouts_and_rendering.html, does not work for me

在http://guides.rubyonrails.org/layouts_and_rendering.html 的名为“Layouts and Rendering in Rails”的 Ruby On Rails 指南中，将 :alert（或 :notice）与渲染方法一起使用对我不起作用

That's the sample code provided in the guide:

这是指南中提供的示例代码：

    def index
      @books = Book.all
    end

    def show
      @book = Book.find_by_id(params[:id])
      if @book.nil?
        @books = Book.all
        render "index", :alert => 'Your book was not found!'
      end
    end

I have a hello controller that looks like this:

我有一个 hello 控制器，如下所示：

    class HelloController < ApplicationController
      def index
        @counter = 5
      end
      def bye
        @counter = 4
        render "index", :alert => 'Alert message!'
      end
    end

My index.html.erb view looks like that:

我的 index.html.erb 视图如下所示：

    <ul>
    <% @counter.times do |i| %>
      <li><%= i %></li>
    <% end %>
    </ul>

When accessing http://localhost:3000/hello/bye, I see the index view, i.e. a list of numbers from 1 to 4 as expected, but there's no 'Alert message!' alert showing.

访问时http://localhost:3000/hello/bye，我看到了索引视图，即按预期从 1 到 4 的数字列表，但没有“警报消息！” 警报显示。

My layout uses this to show alert messages:

我的布局使用它来显示警报消息：

    <% flash.each do |k, v| %>
      <div id="<%= k %>"><%= v %></div>
    <% end %>

回答by Dan Wich

I'm confused as to why that Rails Guide mentions using flash values in render, since they only appear to work in redirect_toat the moment. I think you'll find your approach works if you put a flash.now[:alert] = 'Alert message!'before your render method call.

我很困惑为什么 Rails 指南提到在 中使用 flash 值render，因为它们目前似乎只适用redirect_to。如果您flash.now[:alert] = 'Alert message!'在渲染方法调用之前放置一个，我认为您会发现您的方法有效。

Edit: this is a flaw in the guides that will be fixed, you should use the separate method call to set the flash prior to calling render.

编辑：这是将被修复的指南中的一个缺陷，您应该在调用渲染之前使用单独的方法调用来设置 Flash。

回答by PericlesTheo

Try

尝试

  def bye
    @counter  = 4
    flash.now[:error] = "Your book was not found"
    render :index
  end

回答by Karl Wilbur

Normally you would do something like:

通常你会做这样的事情：

if @user.save
  redirect_to users_path, :notice => "User saved"
else
  flash[:alert] = "You haz errors!"
  render :action => :new
end

What you want to do is (and I like this syntax much better):

你想要做的是（我更喜欢这种语法）：

if @user.save
  redirect_to users_path, :notice => "User saved"
else
  render :action => :new, :alert => "You haz errors!"
end

...however, that isn't valid for ActionController::Flash#render.

...但是，这不适用于ActionController::Flash#render.

But, you can extend ActionController::Flash#renderto do exactlywhat you want:

但是，您可以扩展ActionController::Flash#render以完全执行您想要的操作：

Create config/initializers/flash_renderer.rbwith the following content:

config/initializers/flash_renderer.rb使用以下内容创建：

module ActionController
  module Flash

    def render(*args)
      options = args.last.is_a?(Hash) ? args.last : {}

      if alert = options.delete(:alert)
        flash[:alert] = alert
      end

      if notice = options.delete(:notice)
        flash[:notice] = notice
      end

      if other = options.delete(:flash)
        flash.update(other)
      end

      super(*args)
    end

  end
end

Ref: http://www.perfectline.co/blog/2011/11/adding-flash-message-capability-to-your-render-calls-in-rails-3/

参考：http: //www.perfectline.co/blog/2011/11/adding-flash-message-capability-to-your-render-calls-in-rails-3/