Book Image

Beginning Swift

By : Rob Kerr, Kåre Morstøl
Book Image

Beginning Swift

By: Rob Kerr, Kåre Morstøl

Overview of this book

Take your first foray into programming for Apple devices with Swift.Swift is fundamentally different from Objective-C, as it is a protocol-oriented language. While you can still write normal object-oriented code in Swift, it requires a new way of thinking to take advantage of its powerful features and a solid understanding of the basics to become productive.
Table of Contents (10 chapters)

Lazy Operations

All the sequences and methods we have looked at so far this lesson have been eager, which means they perform their operations immediately, and filter, map, and flatMap return their results in arrays. But sometimes, we may want to delay operations until they are needed.

Say you have a very large array, and you want to first use map and then perform other operations. If done eagerly, map will create a new array with the same number of elements as the original one to store its results. But if we do it lazily, map will return a LazyMapSequence, which will perform each map operation directly when asked for, without using any intermediate storage.

Infinite sequences must be handled lazily, as they obviously cannot be stored.

Lazy Sequences

A lazy sequence is one that conforms to LazySequenceProtocol. The original sequence itself may or may not work lazily internally, but some further operations on the sequence...