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Mastering Swift 3
Mastering Swift 3

Mastering Swift 3: Build incredible apps for iOS and OS X

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Mastering Swift 3

Chapter 2. Learning About Variables, Constants, Strings, and Operators

The first program I ever wrote was written in the BASIC programming language and was the typical Hello World application. This application was pretty exciting at first, but the excitement of printing static text wore off pretty quickly. For my second application, I used BASIC's input command to prompt the user for a name and then printed out a custom hello message to the user with their name in it. At the age of 12, it was pretty cool to display Hello Han Solo. This application led me to create numerous Mad Lib style applications that prompted the user for various words and then put those words into a story that was displayed after the user had entered all the required words. These applications introduced me to, and taught me, the importance of variables. Every useful application I created since then has used variables.

In this chapter, we will cover the following topics:

  • What variables and constants...

Constants and variables

Constants and variables associate an identifier (such as myName or currentTemperature) with a value of a particular type (such as String or Int), where the identifier can be used to retrieve the value. The difference between a constant and a variable is that a variable can be updated or changed, while a constant cannot be changed once a value is assigned to it.

Constants are good for defining the values that you know will never change, such as the temperature that water freezes at or the speed of light. Constants are also good for defining a value that we use many times throughout our application, such as a standard font size or the maximum number of characters in a buffer. There will be numerous examples of constants throughout this book, and it is recommended that we use constants rather than variables whenever possible.

Variables tend to be more common in software development than constants. This is mainly because developers tend to prefer variables to constants...

Operators

An operator is a symbol or combination of symbols that we can use to check, change, or combine values. We have used operators in most of the examples so far in this book , but we did not specifically call them operators. In this section, we will show how to use most of the basic operators that Swift supports.

Swift supports most standard C operators and also improves them to eliminate several common coding errors. For example, the assignment operator does not return a value, which prevents it from being used where we meant to use the equality operator (==).

Let's look at the operators in Swift.

The assignment operator

The assignment operator initializes or updates a variable.

Prototype:

varA = varB 

Example:

let x = 1 
var y = "Hello" 
a = b 

Comparison operators

The comparison operator returns a Boolean true if the statement is true or a Boolean false if the statement is not true.

Prototypes:

Equality:  varA == varB 
Not equal:  varA != varB 
Greater than:  varA > varB...

Summary

In this chapter, we covered a lot of different topics. These topics ranged from variables and constants to data types and operators. The items in this chapter will be the foundation of every application that you write; therefore, it is important to understand the concepts discussed here.

In the next chapter, we will look at how we can use Swift collection types to store related data. These collection types are the dictionary and array types. We will also look at how we can use the Cocoa and Foundation data types in Swift.

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Key benefits

  • • Discover the new features and improvements to Swift 3
  • • Get to grips with advanced design patterns and techniques to write smarter, cleaner Swift code
  • • Become a more fluent Swift developer and build powerful, impressive iOS and OS X applications.

Description

Swift is the definitive language of Apple development today. It’s a vital part of any iOS and OS X developer’s skillset, helping them to build the most impressive and popular apps on the App Store—the sort of apps that are essential to iPhone and iPad users every day. With version 3.0, the Swift team have added new features to improve the development experience—making it easier to get the results you want and customers expect. Inside, you’ll find the key features of Swift 3.0 and quickly learn how to use the newest updates to your development advantage. From Objective-C interoperability to ARC, to closures and concurrency, this advanced Swift guide will develop your expertise and make you more fluent in this vital programming language. We give you in-depth knowledge of some of the most sophisticated elements of Swift development including protocol extensions, error-handling, design patterns, and concurrency, and guide you on how to use and apply them in your own projects. You'll see how even the most challenging design patterns and programming techniques can be used to write cleaner code and to build more performant iOS and OS X applications. By the end of this book, you’ll have a handle on effective design patterns and techniques, which means you’ll soon be writing better iOS and OS X applications with a new level of sophistication and control.

Who is this book for?

This book is for developers who want to dive into the newest version of Swift. 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.

What you will learn

  • Dive into the core components of Swift 3.0, including operators, collections, control flow, and functions
  • Create and use classes, structures, and enums
  • Understand object-oriented Swift and see how to tackle inheritance, protocols, and extensions
  • Develop a practical understanding of subscripts, optionals, and closures
  • See how to use the new protocol extension and error handling features of Swift 3.0
  • Add concurrency to your applications using Grand Central Dispatch

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Oct 25, 2016
Length: 392 pages
Edition : 1st
Language : English
ISBN-13 : 9781786466129
Vendor :
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Product Details

Publication date : Oct 25, 2016
Length: 392 pages
Edition : 1st
Language : English
ISBN-13 : 9781786466129
Vendor :
Apple
Category :
Languages :
Tools :

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Table of Contents

17 Chapters
1. Taking the First Steps with Swift Chevron down icon Chevron up icon
2. Learning About Variables, Constants, Strings, and Operators Chevron down icon Chevron up icon
3. Using Swift Collections and the Tuple Type Chevron down icon Chevron up icon
4. Control Flow and Functions Chevron down icon Chevron up icon
5. Classes and Structures Chevron down icon Chevron up icon
6. Using Protocols and Protocol Extensions Chevron down icon Chevron up icon
7. Protocol-Oriented Design Chevron down icon Chevron up icon
8. Writing Safer Code with Availability and Error Handling Chevron down icon Chevron up icon
9. Custom Subscripting Chevron down icon Chevron up icon
10. Using Optional Types Chevron down icon Chevron up icon
11. Working with Generics Chevron down icon Chevron up icon
12. Working with Closures Chevron down icon Chevron up icon
13. Using Mix and Match Chevron down icon Chevron up icon
14. Concurrency and Parallelism in Swift Chevron down icon Chevron up icon
15. Swift Formatting and Style Guide Chevron down icon Chevron up icon
16. Swifts Core Libraries Chevron down icon Chevron up icon
17. Adopting Design Patterns in Swift Chevron down icon Chevron up icon

Customer reviews

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j4nnis Jan 18, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I was the technical reviewer for this book. This means I had a minor role in the production of this book. But it also means that i did read earlier drafts of this book fairly thoroughly. I can't very well give a comment on typos because I did not read the final version of every chapter. So my short review:The book gives a good introduction to Swift in it’s most current iteration. It explains critical concepts of the language like optionals, generics and closures without over-complicating them. Being a book specifically on Swift 3 it points out differences between earlier version of the language and this most current one. Jon’s style of writing is easy to follow and understand.I especially liked that the book does a detour and suggest how a few common design patterns could sensibly be adopted in Swift 3. For programmers coming from other languages this can be valuable as it shows familiar functionality done with a new set of tools.Although Swift 3 does not contain any language level concurrency Mastering Swift 3 explains existing technologies to deal with asynchronous problems. This includes an introduction to Grand Central Dispatch and Operation queues.I think the book does a good job of giving the reader an intoduction to Swift and to real world programming in this language.
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Dharma Kshetri Jan 20, 2018
Full star icon Full star icon Full star icon Full star icon Full star icon 5
lots of real-world examples and useful resources for learning swift3. I would like to highly recommended to all of developers, who want to learn swift 3.
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JMcDivitt Jan 14, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Great Resource and learning material
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Sandeep Mahajan Apr 23, 2018
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Awesome book.
Amazon Verified review Amazon
Matthew Whillock Mar 27, 2017
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Very good book, seems to cover everything in a readable style.
Amazon Verified review Amazon
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