Default Controller Params

On occasion you may need to assign default values to the params required within a controller. For example, assume we’re working with todos and we want to assign a todo to the current user (by default, unless another user is specified), then I’ve usually seen some people handle default param values like this:

def todo_params
  params
    .require(:todo)
    .permit(:subject, :description, :user_id)
    .tap { |pms|  pms.user_id ||= current_user.id }
end

However, TIL that you can actually make use of a method called with_defaults:

def todo_params
  params
    .require(:todo)
    .permit(:subject, :description, :user_id)
    .with_defaults(user_id: current_user.id)
end

Much cleaner!

Also, with_defaults is defined for ActionController::Parameters and Hash. I find with_defaults much cleaner, and more intention revealing, than reverse_merge!