Custom Flash Messages in Rails

Why Aren't My Flash Messages Working?

Turns out, there's 2 keys that Rails supports by default for flash messages. Those are alert and notice; you can use them like this in your controller:

redirect_to users_path, notice: "User created successfully"
# - or -
render :new, alert: "An error prevented the user from being saved"

But if your flash rendering code is generic enough, you might notice that explicitly setting a key/message on flash will work for values other than the defaults:

flash[:success] = "User created successfully"
redirect_to users_path

TIL Rails has a helper that will allow us to add our own custom flash messages - add_flash_type. You can use this an a controller (re: ApplicationController) to enable new flash message types. This will allow you to do the one liners in render and redirect calls:

class ApplicationController < ActionController::Base
  add_flash_type :my_flash_type
end

# ...

redirect_to users_path, my_flash_type: "User created successfully"
# - or -
render :new, my_flash_type: "An error prevented the user from being saved"

In addition, it will also add a variable in our views to retrieve this message:

<%= my_flash_type %>

https://api.rubyonrails.org/classes/ActionController/Flash/ClassMethods.html