Register your own flash types - Rails 4

In Rails 3, the ability to set flash parameters :notice and :alert in a controllerredirect_to call was added. Along with this change,ActionController::Base#notice andActionController::Base#alert were added as convenience accessors, which mapped to flash[:notice] and flash[:alert] respectively.

To set a custom flash type in your controller, you would have add the key/value pair to the controller flash hash, or you could also pass a hash to the optional :flashoption in redirect_to.

As of Rails 4, developers will have the ability to register their own flash types by using the new ActionController::Flash.add_flash_types macro style method.

The Rails 3 Way

Here is an example of setting a custom error flash type in Rails 3:

# app/controllers/users_controller.rb
class UsersController < ApplicationController
  def create
    ...
    flash[:error] = "An error message for the user"
    redirect_to home_path
  end
end

# app/views/home/index
<%= flash[:error] %>

The Rails 4 Way

Here is the same example as above, using Rails 4:

# app/controllers/application_controller.rb
class ApplicationController
    ...
  add_flash_types :error, :another_custom_type
end

# app/controllers/users_controller.rb
class UsersController < ApplicationController
  def create
    ...
    redirect_to home_path,
      error: "An error message for the user"
  end
end

# app/views/home/index
<%= error %>