ActionController::Base has a default flash types of [:notice] allowing you to pass a key to #redirect_to:
class Controller < ActionController::Base
def create
if true
redirect_to root_path, status: :see_other, notice: "Created"
else
flash[:error] = "Could not create"
redirect_to root_path, status: :see_other
end
end
However, you can add :error as a custom type to get the convenience argument:
class Controller < ActionController::Base
add_flash_types :error
def create
if true
redirect_to root_path, status: :see_other, notice: "Created"
else
redirect_to root_path, status: :see_other, error: "Could not create"
end
end