Inheritence or similar technique

[noone0012]

I've got userType that represents the viewer. I'm also using this type when getting viewer's friends.
But some fields are only related to viewer. For example, chatMessageSound: bool, notificationsEmail: bool. So it doesn't make sense to return those fields if it has been queried from friends field.

How to deal with this?
I can check it and return null for all those fields but it isn't best way to do that, so I should convert all non-nullable fields to back.
I also don't want to create seperate 2 types because they have many common fields.
Is there a way to implement it with inheritence?