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Swift 4 Protocol-Oriented Programming

By : Jon Hoffman

4.1 (29)

Swift 4 Protocol-Oriented Programming

4.1 (29)

By: Jon Hoffman

Overview of this book

Swift has become the number one language used in iOS and macOS development. The Swift standard library is developed using protocol-oriented programming techniques, generics, and first-class value semantics; therefore, every Swift developer should understand these powerful concepts and how to take advantage of them in their application design. This book will help you understand the differences between object-oriented programming and protocol-oriented programming. It will demonstrate how to work with protocol-oriented programming using real-world use cases. You will gain a solid knowledge of the various types that can be used in Swift and the differences between value and reference types. You will be taught how protocol-oriented programming techniques can be used to develop very flexible and easy-to-maintain code. By the end of the book, you will have a thorough understanding of protocol-oriented programming and how to utilize it to build powerful and practical applications.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

Starting with the Protocol

Starting with the Protocol

Protocol syntax

Protocol inheritance

Protocol composition

Using protocols as a type

Polymorphism with protocols

Type casting with protocols

Associated types with protocols

Delegation

Designing with protocols

Protocols in the Swift standard library

Summary

Our Type Choices

Our Type Choices

Classes

Structures

Access controls

Enumerations

Tuples

Protocols

Value and reference types

Recursive data types for reference types only

Inheritance for reference types only

Dynamic dispatch

Swift's built-in types

Copy-on-write

Summary

Extensions

Extensions

Defining an extension

Protocol extensions

Text validation

Extensions with the Swift standard library

Conforming to the Equatable protocol

Summary

Generics

Generics

Generic functions

Type constraints with Generics

Generic types

Associated types

Generic subscripts

Copy-on-write

Generics in a protocol-oriented design

Generics in the Swift standard library

Summary

Object-Oriented Programming

Object-Oriented Programming

What is object-oriented programming?

Requirements for the sample code

Swift as an object-oriented programming language

Issues with the object-oriented design

Summary

Protocol-Oriented Programming

Protocol-Oriented Programming

Requirements for the sample code

Swift as a protocol-oriented programming language

Summarizing protocol-oriented programming and object-oriented programming

Differences between object-oriented programming and protocol-oriented programming

The winner is...

Summary

Adopting Design Patterns in Swift

Adopting Design Patterns in Swift

What are design patterns?

Creational patterns

Structural design patterns

Behavioral design patterns

Summary

Case Studies

Case Studies

Logging service

Data access layer

Summary

Customer Reviews

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Generic subscripts

Prior to Swift version 4, we could use generics with subscripts only if the generic was defined in the containing type, however we were unable to define a new generic type within the subscript definition. For example, if we had a List type we could use the generic type defined by the List type within the subscript as shown in this example:

struct List<T> { 
  /*  other implementation code here */ 
 
  subscript(index: Int) -> T? { 
    return getItemAtIndex(index: index) 
  } 
}

With Swift version 4 and later, we are able to define generic types within the subscript definition itself. To see how we would do this, let's go ahead and create another very basic generic List type. The following code shows how to do this:

struct List<T> { 
  private var items = [T]() 
  public mutating func add(item: T) { 
    items.append(item) 
  } 
  public func getItemAtIndex(index: Int) -> T? { 
    if items.count > index { 
      return items[index] 
    } else { 
 ...

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