August 1, 2014 by Daniel P. Clark

Manual Polymorphic Creation in Rails

Finding documentation online to do this was pretty much a no go.  The answer I’ve provided here was grasped from hints given on many websites of what could be done but without anything I could really sink my teeth into.

What this code allows you to accomplish is to create a belongs_to/has_many relationship to something while maintaining only one of each kind.

If something will, or may, have more than one belongs_to relationship, then you should use polymorphic relationships. The available online documentation on that pretty much just covers the basics.  So I hope that this code outline will give you a deeper understanding and find success with polymorphic relationships with Rails from here on forward!




I’ve shortened the actual file for just what’s relevant here. You will need any other parameters permitted for your use case. The rest can remain untouched.


This is where the magic will happen. It’s designed after .where(…).first_or_create but uses build instead so we don’t have to declare build for the socials object in the profile_controller.

And lastly the all important view:

(polymorphics most undocumented aspect.)



The @social_list is defined in the profile_controller and is an array of label & kind pairs. So as each one gets passed through, the one_by_kind method we defined in the application_controller seeks for the first polymorphic child that has the right kind which we’ve named entry. If the database record isn’t found, it is then built. one_by_kind then hands back the object for us to write/update.

This maintains one view for both creating and updating polymorphic children. So it allows for a one of each kind within your profile and social relation.

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God Bless! – Daniel P. Clark

#diy#howto#manual#one to many#polymorphic#rails#ruby on rails