How it works...

We started by defining VehicleProtocol that has a list of properties and functions that every vehicle should have. In properties, we have two types of properties: name, which is marked as {get set}, and canFly, which is marked as {get}. When you mark a property {get set}, it means it's gettable and settable, whereas {get} means it only gettable, in other words, it's a read-only property. Then, we added four methods, out of which three methods-numberOfWheels(), move(), and stop()-are instance methods. The last one-popularBrands()- marked as static is a type method. Types methods can be called directly with type name, and there is no need to have instance to call it.

Then, we created two new classes, Bicycle and Car, which conform to VehicleProtocol, and each one will have different implementations.