How to create a lazy loaded property in Ruby for a Model?

I want to create a lazy-loaded property that returns a collection on a Model, how do I do this?

I don't want to create an association for this.

So I want it to return a collection, if the collection hasn't been initialized yet then hit the database, return the rows, then initialize it.

If it get's run once, then no need to run it again since the next page request will start things over.