Swift Functional Programming - Second Edition

Classes

A class defines a set of properties and suitable operations. From a type-safe programming language point of view, a class is a structure to implement a user-defined type, such as our User class in the preceding example.

Preferably, a class should be an implementation of an Abstract Data Type (ADT) that hides the implementation details.

An implementation of an ADT as a class can be composed of two kinds of method:

• Methods that return meaningful abstractions about the state of an instance
• Transformational methods to move from a valid instance state to another valid state

To be able to hide implementation details and for the sake of abstraction, all the data within a class should be private to the class.

Let's improve the abstraction ...