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:

```ruby
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`:

```ruby
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`!

douglasgreyling
July 18, 2022