Get Ruby class constant dynamically by name

Question

I have a class API that pulls objects from a third party API and builds them into objects that are subclasses of type APIObject. APIObject subclasses match the object names from the API that I'm pulling from:

User < APIObject Account < APIObject 

I would like to define a class method in APIObject that allows me to pull objects using standard Rails accessors:

user = User.find id 

I would like the method to translate this call into an API call like this:

API::User::findById id 

I would like to access the name of the APIObject subclass (User) using self.class.name and use that to call the constant (API::User), but I know API::self.class.name won't work. I could rewrite this method over and over again for every subclass, but it seems like this should be possible without doing that. Suggestions?

Answer 1

I think you’re looking for const_get. Perhaps something like:

def self.find(id)   API.const_get(self.name).find_by_id(id) end 

(note you only need self.name, since this is already in the context of the class, and self.class.name will just be Class).