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 observer pattern


The observer pattern is used when many objects need to listen to changes in one or many other objects.

NotificationCenter is one of the oldest APIs in Foundation, available since macOS 10+ and iOS 2.0, and is used to implement the observer pattern quickly and safely. Using NSObject, it is also possible to use Key-Value Observing (KVO) to observe changes in objects.

In pure Swift, however, you will need to use a third-party object as the NotificationCenter in order to listen to change events. Swift also provides a simple observation mechanism that notifies you when local values are updated.

Event-based programming

Observation is a popular programming strategy that lets you derive the current state of your application from the events you're listening to. Instead of polling for new information, your program will listen to events or notifications in order to update its state.

This strategy is particularly suitable for decoupling event sources from their consumption part. However...