Factory Method

Factory Method: a method picks the concrete class

Problem: callers should ask for what they want, not know which class builds it.

PawWalk scenario: a booking update goes out over email, SMS, or push. A single notifier_for(channel) returns the right notifier; the rest of the code just calls .notify.

In Ruby this is often a plain case in one method — no Creator subclass hierarchy needed. That IS the factory method.