`ActiveRecord::Relation`'s have quite a few awesome helpers that will allow you to treat them almost like a regular model.

You can do stuff like `self.resources.where(attribute: "value")` and it will scope the resources to only resources which belong to this topic.

Similarly, `self.resources.create(attrubte: "value")` will create a resource that belongs to the current topic.

[More details](http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html)