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Home > Programming > High Performance Programming > Swift High Performance
Swift High Performance
Swift High Performance

Swift High Performance: Leverage Swift and enhance your code to take your applications to the next level

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Swift High Performance

Chapter 2. Making a Good Application Architecture in Swift

Swift is a high-performance programming language, as you learned in the previous chapter. You also learned that writing good code is even more important than making it high-performance code. In this chapter, we will put the all-powerful features of Swift together and create an application. We will do this by covering the following topics:

  • Writing clean code
  • Immutability
  • Value types and immutability
  • Representing the state with classes
  • Representing the absence of values with optionals
  • Functional programming
  • Generics

Making a Swift application

The first step in creating a good application architecture is to create the application itself. We will be creating an iOS journal application used to make daily notes. We are not going to cover any iOS-specific topics, so you can use the same code and create OS X applications as well.

Go ahead! Open Xcode and create a new iOS single-view project application. Now, we are ready for coding.

First, let's create a Person type, for the owner of the journal, and a journal entry type. We will use the Class type to create both Person and JournalEntry. Both classes are very simple—just a bunch of properties and an initializer:

class Person {
  var firstName: String
  var lastName: String

  init (firstName: String, lastName: String) {
    self.firstName = firstName
    self.lastName = lastName
  }
 }

class JournalEntry {
  var title: String
  var text: String
  var date: NSDate
  
  init (title: String, text: String) {
    self.title = title
    self.text =...

The differences between variables and constants

Probably, the most often used feature in all programming languages is creating and storing a value. We create local variables in functions and declare them in classes and other data structures; that's why it's very important to do it properly.

In Swift, there are two ways of creating and storing a value, as follows:

  • Making it a variable:
    var name = "Sara"
  • Making it a constant:
    let name = "Sara"

The difference between variables and constants is that a constant value can be assigned only once and can't be changed after that. A variable value, on the other hand, can be changed anytime. Here's an example:

var name = "Sam"
name = "Jon"

let lastName = "Peterson"
lastName = "Jakson" //Error, can't change constant after assigning

Tip

The golden rule is to always declare your type as a constant (the let keyword in the previous example) first. Change it to a variable (the var...

Immutability

In the previous section, you learned how important it is to use immutable constants. There are more immutable types in Swift, and you should take advantage of them and use them. The advantages of immutability are as follows:

  • It removes a bunch of issues related to unintentional value changes
  • It is a safe multithreading access
  • It makes reasoning about code easier
  • There is an improvement in performance

By making types immutable, you add an extra level of security. You deny access to mutating an instance. In our journal app, it's not possible to change a person's name after an instance has been created. If, by accident, someone decides to assign a new value to the person's firstName, the compiler will show an error:

var person = Person(firstName: "Jon", lastName: "Bosh")
p.firstName = "Sam" // Error

However, there are situations when we need to update a variable. An example could be an array; suppose you need to add a new item to it. In our...

Value types and immutability

There are two different data types in Swift:

  • Reference types
  • Value types

Let's take a look at these.

Reference types

A class is a reference type. When you create an instance of a reference type and assign it to a variable or constant, you are not only assigning a value but also a reference that points to the value, which is located somewhere else (actually it is located in the heap memory). When you pass that reference to other functions and assign it to other variables, you are creating multiple references that point to the same data. If one of those variables changes the data, that change will reflect in all other variables as well. Here's an example that shows this:

let person = Person(firstName: "Sam", lastName: "Jakson")
let a = person, b = person, c = person

The following diagram shows what the memory for this code would look like:

Reference types

All four constants would refer to the same object. The danger in this architecture is that if one of...

Representing the absence of values with optionals

Let's go back to the past and see how the absence of a value is represented in Objective-C, as an example. There isn't a standard solution for representing the absence of a value for both reference and simple value types. There are two different ways:

  • nil
  • 0, -1, INT_MAX, NSNotFound, and so on

For reference types, Objective-C uses the nil value to represent that a variable doesn't have a value. It points to nowhere.

For value types, there is no such value as nil and it is not possible to assign nil to an integer variable. To do that, Objective-C (and not only Objective-C but also C, Java, and many other languages) uses a few special values that are unlikely to be the result of a particular operation. For example, the indexOfObject method of NSArray would return NSNotFound.

Note

NSNotFound is just a constant and its value is equal to NSIntegerMax, whose value, in turn, is 2147483647.

Swift uses an optional to represent the absence...

Making a Swift application

The first step in creating a good application architecture is to create the application itself. We will be creating an iOS journal application used to make daily notes. We are not going to cover any iOS-specific topics, so you can use the same code and create OS X applications as well.

Go ahead! Open Xcode and create a new iOS single-view project application. Now, we are ready for coding.

First, let's create a Person type, for the owner of the journal, and a journal entry type. We will use the Class type to create both Person and JournalEntry. Both classes are very simple—just a bunch of properties and an initializer:

class Person {
  var firstName: String
  var lastName: String

  init (firstName: String, lastName: String) {
    self.firstName = firstName
    self.lastName = lastName
  }
 }

class JournalEntry {
  var title: String
  var text: String
  var date: NSDate
  
  init (title: String, text: String) {
    self.title = title
    self.text = text
    date...

The differences between variables and constants

Probably, the most often used feature in all programming languages is creating and storing a value. We create local variables in functions and declare them in classes and other data structures; that's why it's very important to do it properly.

In Swift, there are two ways of creating and storing a value, as follows:

  • Making it a variable:

    var name = "Sara"

  • Making it a constant:

    let name = "Sara"

The difference between variables and constants is that a constant value can be assigned only once and can't be changed after that. A variable value, on the other hand, can be changed anytime. Here's an example:

var name = "Sam"
name = "Jon"

let lastName = "Peterson"
lastName = "Jakson" //Error, can't change constant after assigning

Tip

The golden rule is to always declare your type as a constant (the let keyword in the previous example) first. Change it to a variable (the var keyword) only if you need it afterwards.

There are some exceptions when you can't declare...

Immutability

In the previous section, you learned how important it is to use immutable constants. There are more immutable types in Swift, and you should take advantage of them and use them. The advantages of immutability are as follows:

  • It removes a bunch of issues related to unintentional value changes

  • It is a safe multithreading access

  • It makes reasoning about code easier

  • There is an improvement in performance

By making types immutable, you add an extra level of security. You deny access to mutating an instance. In our journal app, it's not possible to change a person's name after an instance has been created. If, by accident, someone decides to assign a new value to the person's firstName, the compiler will show an error:

var person = Person(firstName: "Jon", lastName: "Bosh")
p.firstName = "Sam" // Error

However, there are situations when we need to update a variable. An example could be an array; suppose you need to add a new item to it. In our example, maybe the person wants to change a...

Value types and immutability

There are two different data types in Swift:

  • Reference types

  • Value types

Let's take a look at these.

Reference types

A class is a reference type. When you create an instance of a reference type and assign it to a variable or constant, you are not only assigning a value but also a reference that points to the value, which is located somewhere else (actually it is located in the heap memory). When you pass that reference to other functions and assign it to other variables, you are creating multiple references that point to the same data. If one of those variables changes the data, that change will reflect in all other variables as well. Here's an example that shows this:

let person = Person(firstName: "Sam", lastName: "Jakson")
let a = person, b = person, c = person

The following diagram shows what the memory for this code would look like:

All four constants would refer to the same object. The danger in this architecture is that if one of those constants updates a piece...

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Page 1 of 10

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Key benefits

  • • Build solid, high performance applications in Swift
  • • Increase your efficiency by getting to grips with concurrency and parallel programming
  • • Use Swift to design performance-oriented solutions

Description

Swift is one of the most popular and powerful programming languages for building iOS and Mac OS applications, and continues to evolve with new features and capabilities. Swift is considered a replacement to Objective-C and has performance advantages over Objective-C and Python. Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible, and more fun. Develop Swift and discover best practices that allow you to build solid applications and optimize their performance. First, a few of performance characteristics of Swift will be explained. You will implement new tools available in Swift, including Playgrounds and REPL. These will improve your code efficiency, enable you to analyse Swift code, and enhance performance. Next, the importance of building solid applications using multithreading concurrency and multi-core device architecture is covered, before moving on to best practices and techniques that you should utilize when building high performance applications, such as concurrency and lazy-loading. Finally, you will explore the underlying structure of Swift further, and learn how to disassemble and compile Swift code.

Who is this book for?

This book is aimed at experienced Swift developers wanting to optimize their programs on Apple platforms to optimize application performance.

What you will learn

  • Build solid, stable, and reliable applications using Swift
  • Use REPL and Pl to manage and configure relational databases
  • Explore Swift s features including its static type system, value objects, and functional programming
  • Design reusable code for high performance in Swift
  • Use to Xcode LLBD and REPL to debug commands
  • Avoid sharing resources by using concurrency and parallel programming
  • Understand the lazy loading pattern, lazy sequences, and lazy evolution.

Product Details

Country selected
Publication date, Length, Edition, Language, ISBN-13
Publication date : Nov 06, 2015
Length: 212 pages
Edition : 1st
Language : English
ISBN-13 : 9781785282201
Category :
Programming
Languages :
Swift
Concepts :
High Performance Programming

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Product Details

Publication date : Nov 06, 2015
Length: 212 pages
Edition : 1st
Language : English
ISBN-13 : 9781785282201
Category :
Programming
Languages :
Swift
Concepts :
High Performance Programming

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Table of Contents

9 Chapters
1. Exploring Swift's Power and Performance Chevron down icon Chevron up icon
1. Exploring Swift's Power and Performance
Swift speed
Welcome to Swift
Swift's features and benefits
Swift interoperability
Performance – meaning and key metrics
Summary
2. Making a Good Application Architecture in Swift Chevron down icon Chevron up icon
2. Making a Good Application Architecture in Swift
Making a Swift application
The differences between variables and constants
Immutability
Value types and immutability
Representing the absence of values with optionals
Functional programming
Generics
Safety
Summary
3. Testing and Identifying Slow Code with the Swift Toolkit Chevron down icon Chevron up icon
3. Testing and Identifying Slow Code with the Swift Toolkit
REPL
Playgrounds
LLDB
REPL in Xcode
Console logs
Performance measuring in unit tests
Instruments
A reminder
Summary
4. Improving Code Performance Chevron down icon Chevron up icon
4. Improving Code Performance
Understanding performance optimization
Optimization checklist
Swift code compilation
Constants and variables
Method calls
Intelligent code
Improving speed
Value objects and reference objects
Swift arrays and unsafe C arrays
Avoiding Objective-C
Summary
5. Choosing the Correct Data Structure Chevron down icon Chevron up icon
5. Choosing the Correct Data Structure
An overview of data structures
Collection types
Swift standard library collections
Collection memory allocation
The CollectionType protocol methods
Accelerate and Surge
Other collections
Summary
6. Architecting Applications for High Performance Chevron down icon Chevron up icon
6. Architecting Applications for High Performance
Achieving high performance
Concurrency overview
Designing asynchronous code
Avoiding state
Divide and conquer
Controlling the lifetime
Summary
7. The Importance of Being Lazy Chevron down icon Chevron up icon
7. The Importance of Being Lazy
The lazy mindset
Lazy loading
Lazy collections and evaluation
Summary
8. Discovering All the Underlying Swift Power Chevron down icon Chevron up icon
8. Discovering All the Underlying Swift Power
How Swift is so fast
Swift command line tools
The Swift compiler
The Swift compilation process and swiftc
Analyzing executable files
Summary
Final thoughts
Index Chevron down icon Chevron up icon
Index

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Michael Roth Dec 04, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Very helpful book. Filled in the gaps to swift ideals that are only glossed over in other books. You do need some exposure to swift to get the most from it, but still a good reference for beginners as well as seasoned swift converts.
Amazon Verified review Amazon
Larry Ball Jan 02, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book does a good job of covering the concepts that affect application performance. These concepts could be applied to other programming languages as well. Coverage of the Swift Toolkit is invaluable. This is a must have book if you want to take your coding from beginning or intermediate to advanced. Even advanced programmers would find it valuable as a reference.
Amazon Verified review Amazon
Gabriel Aguilera Sep 05, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
lots of tips for intermediate Swift programmers. This is my second Swift Language book after the excellent "Swift Programming" by Big Nerd Ranch.
Amazon Verified review Amazon
Michael Jan 03, 2016
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
I was initially concerned that my limited production Swift experience (so far) would hinder the usefulness of this book but the gentle, unassuming nature of the writing soon made that concern dissipate. Instead I got a behind the scenes look at what Swift is, what it does well, and why - from the basics up. In knowing these things, you are then prepared for the second half of the book which helps you to think at the architectural level about programming in Swift.The style is a little informal, and it seems that maybe English is a second language for the author, which may be an issue for some readers. I found it to be endearing and allowed the obvious love that the writer has for Swift, and for programming in general, to come though. It felt more like he was talking to me, instead of lecturing or essaying.Given I have page after page of highlights to go back and review, refer to and turn into a crib sheet, I think it's a worthwhile read for everyone wishing to take their Swift developer skills to the next level. Perhaps not essential, but certainly highly beneficial.
Amazon Verified review Amazon
Andrea Dec 09, 2015
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
If you like going deeper into a language and missed the kind of insights into optimization you can get for other language, this is the book for you.Swift is getting more and more mature and a guide like this is what was actually missing as you often end up asking yourself if what you're doing is the most efficient thing.Probably not a good fit for a complete beginner, but you don't need to be a guru either to appreciate it.
Amazon Verified review Amazon

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About the author

Profile icon Koval
Koval
Github icon
Kostiantyn Koval is a passionate developer with 5 years of experience. All the time, his main passion and work has been building iOS applications. So far, he has built many different applications, including games, enterprise apps, and big platforms. He fell in love with Swift the first minute he saw it, and keeps expressing this to the rest of the world. Other than iOS, he is also interested in technologies and languages such as Scala, Clojure, LLVM, Ruby, JavaScript, and others. He loves open source and blogging. You can find him on GitHub at https://github.com/kostiakoval and his blogs at https://medium.com/@kostiakoval. Other places to contact him are http://kostiakoval.github.io and Twitter at @KostiaKoval. His hobbies are programming, building start-ups, and making this world better with software.
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Can I download the code files for Early Access titles? Chevron down icon Chevron up icon

We try to ensure that all books in Early Access have code available to use, download, and fork on GitHub. This helps us be more agile in the development of the book, and helps keep the often changing code base of new versions and new technologies as up to date as possible. Unfortunately, however, there will be rare cases when it is not possible for us to have downloadable code samples available until publication.

When we publish the book, the code files will also be available to download from the Packt website.

How accurate is the publication date? Chevron down icon Chevron up icon

The publication date is as accurate as we can be at any point in the project. Unfortunately, delays can happen. Often those delays are out of our control, such as changes to the technology code base or delays in the tech release. We do our best to give you an accurate estimate of the publication date at any given time, and as more chapters are delivered, the more accurate the delivery date will become.

How will I know when new chapters are ready? Chevron down icon Chevron up icon

We'll let you know every time there has been an update to a course that you've bought in Early Access. You'll get an email to let you know there has been a new chapter, or a change to a previous chapter. The new chapters are automatically added to your account, so you can also check back there any time you're ready and download or read them online.

I am a Packt subscriber, do I get Early Access? Chevron down icon Chevron up icon

Yes, all Early Access content is fully available through your subscription. You will need to have a paid for or active trial subscription in order to access all titles.

How is Early Access delivered? Chevron down icon Chevron up icon

Early Access is currently only available as a PDF or through our online reader. As we make changes or add new chapters, the files in your Packt account will be updated so you can download them again or view them online immediately.

How do I buy Early Access content? Chevron down icon Chevron up icon

Early Access is a way of us getting our content to you quicker, but the method of buying the Early Access course is still the same. Just find the course you want to buy, go through the check-out steps, and you’ll get a confirmation email from us with information and a link to the relevant Early Access courses.

What is Early Access? Chevron down icon Chevron up icon

Keeping up to date with the latest technology is difficult; new versions, new frameworks, new techniques. This feature gives you a head-start to our content, as it's being created. With Early Access you'll receive each chapter as it's written, and get regular updates throughout the product's development, as well as the final course as soon as it's ready.We created Early Access as a means of giving you the information you need, as soon as it's available. As we go through the process of developing a course, 99% of it can be ready but we can't publish until that last 1% falls in to place. Early Access helps to unlock the potential of our content early, to help you start your learning when you need it most. You not only get access to every chapter as it's delivered, edited, and updated, but you'll also get the finalized, DRM-free product to download in any format you want when it's published. As a member of Packt, you'll also be eligible for our exclusive offers, including a free course every day, and discounts on new and popular titles.