10. Working with Closures | Mastering Swift

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Table Of Contents

Mastering Swift

By : Jon Hoffman

5 (2)

Mastering Swift

5 (2)

By: Jon Hoffman

Overview of this book

If you are a developer that learns best by looking at, and working with, code, then this book is for you. A basic understanding of Apple's tools is beneficial but not mandatory.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Taking the First Steps with Swift

1. Taking the First Steps with Swift

What is Swift?

Playgrounds

Swift language syntax

Hello world

Summary

2. Learning about Variables, Constants, Strings, and Operators

2. Learning about Variables, Constants, Strings, and Operators

Constants and variables

Defining constants and variables

Numeric types

The Boolean type

The string type

Optional variables

Enumerations

Operators

Summary

3. Using Collections and Cocoa Data Types

3. Using Collections and Cocoa Data Types

Swift collection types

Mutability

Arrays

Dictionaries

Tuples

Using Cocoa data types

Foundation data types

Summary

4. Control Flow and Functions

4. Control Flow and Functions

What we have learned so far

Control flow

Functions

Summary

5. Classes and Structures

5. Classes and Structures

What are classes and structures?

Creating a class or structure

Initializer

Inheritance

Overriding methods and properties

Protocols

Extensions

Memory management

Summary

6. Working with XML and JSON Data

6. Working with XML and JSON Data

XML and JSON

Common files

XML and the NSXMLParser class

Using the NSXMLParserDelegate protocol

Parsing XML documents

XML and manually building XML documents

JSON and NSJSONSerialization

Summary

7. Custom Subscripting

7. Custom Subscripting

Introducing subscripts

Subscripts with Swift arrays

Read and write custom subscripts

Read only custom subscripts

Calculated subscripts

Subscript values

Subscripts with ranges

External names for subscripts

Multidimensional subscripts

When not to use a custom subscript

Summary

8. Using Optional Type and Optional Chaining

8. Using Optional Type and Optional Chaining

Introducing optionals

The need for optional types in Swift

Optional chaining

Summary

9. Working with Generics

9. Working with Generics

Introduction to generics

Generic functions

Generic types

Associated types

Summary

10. Working with Closures

10. Working with Closures

Introducing closures

Simple closures

Shorthand syntax for closures

Using closures with Swift's array algorithms

Standalone closures and good style guidelines

Changing functionality

Select a closure based on results

Strong reference cycles with closures

Summary

11. Using Mix and Match

11. Using Mix and Match

What is mix and match?

Using Swift and Objective-C together in the same project

Summary

12. Concurrency and Parallelism in Swift

12. Concurrency and Parallelism in Swift

Concurrency and parallelism

Summary

13. Swift Formatting and Style Guide

13. Swift Formatting and Style Guide

What is a programming style guide?

Your style guide

Summary

14. Network Development with Swift

14. Network Development with Swift

What is network development?

An overview of the URL session classes

REST web services

Making an HTTP GET request

Making an HTTP POST request

Encoding a URL

Checking network connection

RSNetworking

Summary

15. Adopting Design Patterns in Swift

15. Adopting Design Patterns in Swift

What are design patterns?

Creational patterns

Structural design patterns

Behavioral design patterns

Summary

Index

Index

Changing functionality

Closures also give us the ability to change the functionality of classes on the fly. We saw in Chapter 9, Working with Generics that generics gave us the ability to write functions that are valid for multiple types. With closures, we are able to write functions and classes whose functionality can change based on the closure that is passed into it as a parameter. In this section, we will show how to write a function whose functionality can be changed with a closure.

Let's begin by defining a class that will be used to demonstrate how to swap out functionality. We will name this class TestClass:

class TestClass {
  typealias getNumClosure = ((Int, Int) -> Int)
  
  var numOne = 5
  var numTwo = 8
  
  var results = 0
  func getNum(handler: getNumClosure) -> Void{
    results = handler(numOne,numTwo)
    return results
  }
}

We begin this class by defining a type alias for our closure that is named getNumClosure. Any closure defined as a getNumClosure closure will...

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