Can you resolve an angularjs promise before you return it?

I am trying to write a function that returns a promise. But there are times when the information requested is available immediately. I want to wrap it in a promise so that the consumer doesn't need to make a decision.

function getSomething(id) {
    if (Cache[id]) {
        var deferred = $q.defer();
        deferred.resolve(Cache[id]); // <-- Can I do this?
        return deferred.promise;
    } else {
        return $http.get('/someUrl', {id:id});
    }
}

And use it like this:

somethingService.getSomething(5).then(function(thing) {
    alert(thing);
});

The problem is that the callback does not execute for the pre-resolved promise. Is this a legitimate thing to do? Is there a better way to handle this situation?