Rails 3 - notice and error flash cannot be rendered in a partial

问题

I was trying to clean up application.html.erb, by moving parts of the layout into partials. I had the following code for handling flash errors/notifications:

<div id="flash">
  <% if flash[:notice] %>
    <h3 class="info_box"><%= flash[:notice] %></h3>
  <% end %>
  <% if flash[:error] %>
    <h3 class="error_box"><%= flash[:error] %></h3>
  <% end %> 
</div>

This code worked fine in application.html.erb, until I moved it into a file called "_flash.html.erb" and replaced it with the following:

<%= render 'layouts/flash' %>

In the partial the flash hash was not a recognized object and causes a "You have a nil object when you didn't expect it!" error.

I've move the code back to application.html.erb and all is good. But I couldn't find an answer for accessing the flash hash within a partial. Looking at the Rails Guide for "Rendering and Layouts" I can see that there are various ways for render() to pass variables into the partial, but I was unsuccessful in figuring it out. Any ideas?

回答1:

Goliatone's solution seemed to work, but in the end it didn't. I found out that the reason this was not working for me was that I had named my partial _flash. Apparently Rails creates a local variable for the partial using the partial's name (without the "_" character.) So I had a variable clash. As soon as I change the name of the partial to something other than _flash everything worked perfectly. I found the answer here: Rails flash[:notice] always nil

回答2:

You can place the conditional check for flash in the layout, and if it exists then render the partial:

<%= render 'layouts/flash' unless flash.nil?%>

Then, if it exists it will get rendered as expected.

来源：https://stackoverflow.com/questions/8023396/rails-3-notice-and-error-flash-cannot-be-rendered-in-a-partial