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 flyweight pattern


To conclude this chapter on structural design patterns, we'll dive into the flyweight pattern. You may want to use the flyweight pattern when:

  • You create many instances of the same object
  • You can afford to use memory to cache instances
  • You do not mutate those instances, and can afford to share them across your program

Let's say you want to build an application to help with groceries and recipes. As input, we may have lists of ingredients and their amounts, based on their names, as strings. We want to be able to make lists, organize them, and more.

While we technically could store the strings as our base items, we'll use the flyweight pattern to encapsulate those item names. This will help us be more accurate in the rest of our program. Instead of using strings around, we'll use proper instances.

A shopping list using the flyweight pattern

First, we'll need to identify the object that will be reused over and over in our flyweight pattern—Ingredient:

struct Ingredient: CustomDebugStringConvertible...