The flatMap() method transforms optionals and arrays

About 2 min

The flatMap() method transforms optionals and arrays 관련

HACKING WITH SWIFT

What's new in Swift?

The flatMap() method transforms optionals and arrays | Changes in Swift 1.2

The flatMap() method transforms optionals and arrays

Available from Swift 1.2

The flatMap() method is designed to allow you to transform optionals and elements inside a collection while also decreasing the amount of containment that happens. For example, if you transform an optional in a way that will also return an optional, using map() would give you an optional optional (a double optional), whereas flatMap() is able to combine those two optionals into a single optional.

let lengthOfFirst = names.first.flatMap { count($0) }

Decreasing the amount of containment also makes flatMap() a simple way of converting multi-dimensional arrays into single-dimensional arrays:

[[1, 2], [3, 4], [5, 6]].flatMap { $0 }

There is no "map" operation there, so we're just left with the flattening behavior – that will result in a single array containing the value [1, 2, 3, 4, 5, 6].

Other changes in Swift 1.2…

The zip() function joins two sequences | Changes in Swift 1.2

The zip() function joins two sequences

Closures can now be marked @noescape | Changes in Swift 1.2

Closures can now be marked @noescape

Classes can now have static methods and properties | Changes in Swift 1.2

Classes can now have static methods and properties

Constants no longer require immediate initialization | Changes in Swift 1.2

Constants no longer require immediate initialization

A new Set data structure | Changes in Swift 1.2

A new Set data structure

Implicit bridging has been reduced | Changes in Swift 1.2