Book Image

Hands-On Design Patterns with Swift

By : Florent Vilmart, Giordano Scalzo, Sergio De Simone
Book Image

Hands-On Design Patterns with Swift

By: Florent Vilmart, Giordano Scalzo, Sergio De Simone

Overview of this book

Swift keeps gaining traction not only amongst Apple developers but also as a server-side language. This book demonstrates how to apply design patterns and best practices in real-life situations, whether that's for new or already existing projects. You’ll begin with a quick refresher on Swift, the compiler, the standard library, and the foundation, followed by the Cocoa design patterns – the ones at the core of many cocoa libraries – to follow up with the creational, structural, and behavioral patterns as defined by the GoF. You'll get acquainted with application architecture, as well as the most popular architectural design patterns, such as MVC and MVVM, and learn to use them in the context of Swift. In addition, you’ll walk through dependency injection and functional reactive programming. Special emphasis will be given to techniques to handle concurrency, including callbacks, futures and promises, and reactive programming. These techniques will help you adopt a test-driven approach to your workflow in order to use Swift Package Manager and integrate the framework into the original code base, along with Unit and UI testing. By the end of the book, you'll be able to build applications that are scalable, faster, and easier to maintain.
Table of Contents (22 chapters)
Title Page
Copyright and Credits
About Packt
Contributors
Preface
Index

The memento pattern


The memento pattern is useful if you need to preserve multiple states of your program or models, which you want to be able to go back or forward to, such as a browsing history or an undo manager.

In this section, we'll implement the memento pattern with a simple example that showcases the different objects required for this pattern.

Components of the memento pattern

The memento pattern requires the implementation of three distinct entities:

  • Memento: a representation of the internal state of Originator, which should be immutable
  • Originator: the original object that can produce and consume the Memento, in order to save and restore its own state
  • CareTaker: an external object that stores and restores a Memento to an Originator

Note

Memento, in other languages, may be implemented as an opaque box so the state can't be mutated. In Swift, we can leverage structs, their immutability, and the fact they are passed by value and not reference. It is critical that different Memento objects...