Should a method ending in ? (question mark) return only a boolean?

Question

I think it's just common sense and Ruby convention to do this but I have this method:

def is_subscribed?(feed_url)   Subscription.find_by_user_id_and_feed_id(self[ :id ], Feed.find_by_feed_url(feed_url)) end 

The only confusion I'm getting is, this doesn't return boolean like I originally anticipated by putting the question mark on the end of the method name. I was under the impression that when evaluating an object as conditional it returns true if not nil.

Apparently I'm missing the point here and it's not evaluating it like I thought.

So, my question is, would it be best to just do an if (condition) true else false? Or is there a more elegant method of doing this?

Answer 1

A method ending with ? should return a value which can be evaluated to true or false. If you want to ensure a boolean return, you can do so by adding a double bang to the finder.

def is_subscribed?(feed_url)   !!Subscription.find_by_user_id_and_feed_id(self[ :id ], Feed.find_by_feed_url(feed_url)) end