The flash provides a way to pass temporary objects between actions. Anything you place in the flash will be exposed to the very next action and then cleared out. This is a great way of doing notices and alerts, such as a create action that sets flash[:notice] = "Successfully created" before redirecting to a display action that can then expose the flash to its template. Actually, that exposure is automatically done. Example:

  class PostsController < ActionController::Base
    def create
      # save post
      flash[:notice] = "Successfully created post"
      redirect_to posts_path(@post)

    def show
      # doesn't need to assign the flash notice to the template, that's done automatically

    <% if flash[:notice] %>
      <div class="notice"><%= flash[:notice] %></div>
    <% end %>

This example just places a string in the flash, but you can put any object in there. And of course, you can put as many as you like at a time too. Just remember: They’ll be gone by the time the next action has been performed.

See docs on the FlashHash class for more details about the flash.

Show files where this module is defined (1 file)
Register or log in to add new notes.
November 16, 2008 - (>= v2.1.0)
11 thanks

Application Helper for Fading Flash Messages

A simple helper method for showing the flash message. Includes optional fade in seconds (view needs javascript_include_tag defaults if you desire fade effect):

def show_flash_message(options={})
  html = content_tag(:div, flash.collect{ |key,msg| content_tag(:div, msg, :class => key) }, :id => 'flash-message')
  if options.key?(:fade)
    html << content_tag(:script, "setTimeout(\"new Effect.Fade('flash-message');\",#{options[:fade]*1000})", :type => 'text/javascript')

simply call in your views then using:

<%= show_flash_message(:fade => 4) %>
June 11, 2009
4 thanks

Keeping the flash object on multiple redirects

If your controllers are redirecting more than once, the flash contents will be lost. To avoid it, execute flash.keep before each redirection.

Check ActionController::Flash::FlashHash for more handy methods (discard, now, …)

March 20, 2009
2 thanks

Broadened Flash helper

Building on the below excellent example, you can create something with default options for how long it’s displayed and how long the fade is, and highlight:

def show_flash(options={})
  options = {:fade => 3, :display => 3, :highlight => true}.merge(options)
  html = content_tag(:div, flash.collect{ |key,msg| content_tag(:div, msg, :class => key, :attributes => "style = display: none;") }, :id => 'flash-message')
  html << content_tag(:script, "new Effect.Highlight('flash-message');") if options[:highlight]
  html << content_tag(:script, "$('flash-message').appear();")
  html << content_tag(:script, "setTimeout(\"$('flash-message').fade({duration: #{options[:fade]}});\", #{options[:display]*1000});")
August 5, 2014
0 thanks

Handling flash for ajax calls

This is helper method which can be easily used to handle flash for ajax calls

##call it in your js.erb
def flash_display
response = ""
flash.each do |name, msg|
	msg=msg+"<button type='button' class='close' title='hide' data- dismiss='alert'><i class='fa-times-circle-o fa pull-right'></i></button>".html_safe
  response = response + 
  content_tag(:div, msg, :id => "flash_# {name}",:class=>"alert alert-danger") do 

so in your controller,

def get_data_and_update_div
 if @user_details.nil?
   flash.now[:error]="Add your details and then submit"
   format.js { render   'shared/error_messages'}

in error_messages.js.erb

$('#flash_messages').html("<%= escape_javascript raw(flash_display) %>");

in view file

<div id="flash_messages">
  <% if flash[:error] %>
   <%= content_tag :div, flash['value'], :id =>"flash_error" %>
 <% end %>