Swift 4 Protocol-Oriented Programming - Third Edition

Understanding the solution

With the observer pattern, the observer registers to be notified when an event happens. When the event is triggered, any instance that has registered for the event receives a notification that the event has occurred. In Swift, there are several ways that we can implement the observer pattern and in this section we will look at two of them. We are looking at multiple solutions for this pattern because each of these solutions helps us implement the observer pattern under specific circumstances. We will talk about when to use each one of these solutions as we talk about the solutions themselves.