In order to save space on default field values I've overridden methods in my models to ensure nil values return a default values when read. This works find for all types but Array. When I try to push a new value to the array the new value isn't being set.

Given the following model:

class User
  field :friend_ids, type: Array

  def friend_ids
    read_attribute(:friend_ids) || []
  end
end

When running the following in the console you can see how friend_ids isn't being set properly.

> u = User.new
> u.friend_ids
=> []
> u.friend_ids << '123'
=> ["123"]
> u.friend_ids
=> []

Is there a better way of dealing with this situation or is it a bug that can be fixed?