Rails: How to use custom flash types in controllers

Rails supports alert and notice as default flash types. This allows you to use these keys as options in e.g. redirect_to and as a helper in views e.g. <%= notice %> (instead of flash[:notice]).

class SomeController < ApplicationRecord
  def create
    @user = User.create!
    
    redirect_to user_path(@user), notice: "#{@user} created!" 
  end
end

In case you are using Bootstrap as CSS framework you might also want to support flashes like success. This can be done with the add_flash_types method.

class ApplicationController < ActionController::Base
  add_flash_types :success
end

class SomeController < ApplicationRecord
  def create
    @user = User.create!
    
    # Before adding success as flash type
    # flash[:success] = "#{@user} created!" 
    # redirect_to user_path(@user)

    # After adding success as flash type
    redirect_to user_path(@user), success: "#{@user} created!" 
  end
end