Rails first or initialize by one value, but add more values if created

Question

Take the following for example:

GroupMember.where(:member_id => 4).first_or_initialize

What if I wanted to say something like this-

If GroupMember with a member_id of 4 exists, "find it". Otherwise, create a GroupMember with the member_id of 4 AND a group_id of 7.

So I want the above statement to only check for the member_id - But if it doesn't exist, I want it to create a GroupMember with multiple attributes. How would I write that? I am using rails 4.0.

Answer 1

This also works:

GroupMember.where(member_id: 4).first_or_initialize(group_id: 7) 

The attributes passed to first_or_initialize are only used when it creates the new record, and they're merged with the attributes from the "where" clause.