7. Everything is Connected – Memory Management | Learning Swift

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Learning Swift

By : Andrew J Wagner

4.8 (5)

Learning Swift

4.8 (5)

By: Andrew J Wagner

Overview of this book

If you are looking to build iOS or OS X apps using the most modern technology, this book is ideal for you. You will find this book especially useful if you are new to programming or if you have yet to develop for iOS or OS X.

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. Introducing Swift

1. Introducing Swift

Defining our goals for this book

Setting up the development environment

Running our first Swift code

Understanding playgrounds

Learning with this book

Summary

2. Building Blocks – Variables, Collections, and Flow Control

2. Building Blocks – Variables, Collections, and Flow Control

Core Swift types

Swift's type system

Printing on the console

Control flow

Functions

Bringing it all together

Summary

3. One Piece at a Time – Types, Scopes, and Projects

3. One Piece at a Time – Types, Scopes, and Projects

Structs

Classes

Enumerations

Projects

Extensions

Scope

Access control

Summary

4. To Be or Not to Be – Optionals

4. To Be or Not to Be – Optionals

Introducing optionals

Unwrapping an optional

Optional chaining

Implicitly unwrapped optionals

Debugging optionals

The underlying implementation

Summary

5. A Modern Paradigm – Closures and Functional Programming

5. A Modern Paradigm – Closures and Functional Programming

Functional programming philosophy

Closures

Building blocks of functional programming in Swift

Lazy evaluation

Curried functions

Summary

6. Make Swift Work for You – Protocols and Generics

6. Make Swift Work for You – Protocols and Generics

Protocols

Defining a generic

Extending the existing generics

Putting protocols and generics to use

Summary

7. Everything is Connected – Memory Management

7. Everything is Connected – Memory Management

How data is stored in a computer

Value types versus reference types

Automatic reference counting

Strong reference cycles

Lost objects

Summary

8. Writing Code the Swift Way – Design Patterns and Techniques

8. Writing Code the Swift Way – Design Patterns and Techniques

What is a design pattern?

Behavioral patterns

Structural patterns

Creational patterns

Using associated values effectively

Extending system types to reduce code

Lazy properties

Summary

9. Harnessing the Past – Understanding and Translating Objective-C

9. Harnessing the Past – Understanding and Translating Objective-C

Swift's relationship with Objective-C

The history of Objective-C

Constants and variables

Containers

Control flow

Functions

Types

Projects

Calling Objective-C code from Swift

Using functions

Summary

10. A Whole New World – Developing an App

10. A Whole New World – Developing an App

Conceptualizing the app

Setting up the app project

Configuring the user interface

Running the app

Allowing picture taking

Temporarily saving a photo

Populating our photo grid

Refactoring to respect Model-View-Controller

Permanently saving a photo

Summary

11. What's Next? Resources, Advice, and Next Steps

11. What's Next? Resources, Advice, and Next Steps

Apple's documentation

Forums and blogs

Prominent figures

Podcasts

Summary

Index

Index

Lost objects

It is a great idea to always keep strong reference cycles in mind, but if we are too aggressive with the use of weak and unowned references, we can run into the opposite type of problem, where an object is deleted before we intend to delete it.

Between objects

With an object, this will happen if all the references to the object are weak or unowned. This won't be a fatal mistake if we use weak references, but if this happens with an unowned reference, it will crash your program.

For example, let's look at our earlier example with an extra weak reference:

class SteeringWheel3 {
    weak var car: Car3?
}

class Car3 {
    weak var steeringWheel: SteeringWheel3?
    
    init(steeringWheel: SteeringWheel3) {
        self.steeringWheel = steeringWheel
        self.steeringWheel!.car = self
    }
}

let wheel3 = SteeringWheel3()
let car3 = Car3(steeringWheel: wheel3)

This code is the same as the previous, except that both the car property of SteeringWheel3 and the steeringWheel property...

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Programming languages

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