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Learning Swift

You're reading from   Learning Swift Build a solid foundation in Swift to develop smart and robust iOS and OS X applications

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Product type Paperback
Published in Jun 2015
Publisher Packt
ISBN-13 9781784392505
Length 266 pages
Edition 1st Edition
Languages
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Author (1):
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Andrew J Wagner Andrew J Wagner
Author Profile Icon Andrew J Wagner
Andrew J Wagner
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Toc

Table of Contents (13) Chapters Close

Preface 1. Introducing Swift 2. Building Blocks – Variables, Collections, and Flow Control FREE CHAPTER 3. One Piece at a Time – Types, Scopes, and Projects 4. To Be or Not to Be – Optionals 5. A Modern Paradigm – Closures and Functional Programming 6. Make Swift Work for You – Protocols and Generics 7. Everything is Connected – Memory Management 8. Writing Code the Swift Way – Design Patterns and Techniques 9. Harnessing the Past – Understanding and Translating Objective-C 10. A Whole New World – Developing an App 11. What's Next? Resources, Advice, and Next Steps Index

Strong reference cycles


A strong reference cycle is when two instances directly or indirectly hold strong references to each other. This means that neither object can ever be deleted because both ensure that the other always exists.

This scenario is our first really bad memory management scenario. It is one thing to keep around memory longer than it is needed, but it is a whole different level to create memory that can never be freed up to be reused again. This type of memory problem is called a memory leak because the computer slowly leaks memory until there is no longer new memory available. This is why you will sometimes see a speed improvement after you restart your device. Upon restarting, all of the memory is freed up again. Modern operating systems sometimes find ways to forcefully free up memory; especially, when they completely quit an app, but we cannot rely on this as programmers.

So, how can we prevent these strong reference cycles? First, let's look at what they look like. There...

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