What is the difference when using flash :error, :alert, and :notice?

Question

As the title of the question asks, I am interested in knowing if there is any difference when using flash[:error], flash[:alert], and flash[:

Answer 1

:alert and :notice functionally differ from other keys you invent. FlashHash provides convenience accessors for the two: flash.alert , flash.notice. Rails' preference for these two further rears its way into redirect_to which will only accept :alert, :notice, or :flash.

However, a commit in July 2012 to edge Rails allows the privilege of adding other flash types. Here's an example of adding custom flash types in Rails 4:

# app/controllers/application_controller.rb
class ApplicationController; add_flash_types(:error, :annoyance); end

# app/controllers/monopoly_controller.rb
class MonopolyController < ApplicationController
  def chance
    ...
    redirect_to haha_path, annoyance: "Go directly to jail. Do not pass Go. Do not collect $200."
  end
end

# app/views/haha/index.html.erb
<%= annoyance %>