There is a handy dynamic attribute in active-record called find_or_create_by:
Model.find_or_create_by_<attribute>(:<attribute> => "")
But what if I need to find_or_create by more than one attribute?
Say I have a model to handle a M:M relationship between Group and Member called GroupMember. I could have many instances where member_id = 4, but I don't ever want more than once instance where member_id = 4 and group_id = 7. I'm trying to figure out if it's possible to do something like this:
GroupMember.find_or_create(:member_id => 4, :group_id => 7)
I realize there may be better ways to handle this, but I like the convenience of the idea of find_or_create.
Multiple attributes can be connected with an and
:
GroupMember.find_or_create_by_member_id_and_group_id(4, 7)
(use find_or_initialize_by
if you don't want to save the record right away)
Edit: The above method is deprecated in Rails 4. The new way to do it will be:
GroupMember.where(:member_id => 4, :group_id => 7).first_or_create
and
GroupMember.where(:member_id => 4, :group_id => 7).first_or_initialize
Edit 2: Not all of these were factored out of rails just the attribute specific ones.
https://github.com/rails/rails/blob/4-2-stable/guides/source/active_record_querying.md
Example
GroupMember.find_or_create_by_member_id_and_group_id(4, 7)
became
GroupMember.find_or_create_by(member_id: 4, group_id: 7)