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Learning Swift Second Edition

Learning Swift Second Edition

By : Andrew J Wagner
5 (1)
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Learning Swift Second Edition

Learning Swift Second Edition

5 (1)
By: Andrew J Wagner

Overview of this book

Swift is Apple’s new programming language and the future of iOS and OS X app development. It is a high-performance language that feels like a modern scripting language. On the surface, Swift is easy to jump into, but it has complex underpinnings that are critical to becoming proficient at turning an idea into reality. This book is an approachable, step-by-step introduction into programming with Swift for everyone. It begins by giving you an overview of the key features through practical examples and progresses to more advanced topics that help differentiate the proficient developers from the mediocre ones. It covers important concepts such as Variables, Optionals, Closures, Generics, and Memory Management. Mixed in with those concepts, it also helps you learn the art of programming such as maintainability, useful design patterns, and resources to further your knowledge. This all culminates in writing a basic iOS app that will get you well on your way to turning your own app ideas into reality.
Table of Contents (14 chapters)
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13
Index

Lazy evaluation


A powerful feature of Swift is the ability to make these operations lazily evaluated. This means that, just like a lazy person would do, a value is only calculated when it is absolutely necessary and at the latest point possible.

First, it is important to realize the order in which these methods are executed. For example, what if we only want the first element of our numbers to be mapped to strings:

var firstString = numbers.map({String($0)}).first

This works well, except that we actually converted every number to a string to get to just the first one. That is because each step of the chain is completed in its entirety before the next one can be executed. To prevent this, Swift has a built-in method called lazy.

Lazy creates a new version of a container that only pulls specific values from it when it is specifically requested. This means that lazy essentially allows each element to flow through a series of functions one at a time, as it is needed. You can think about it like...

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