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].
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Other changes in Swift 1.2…
- The zip() function joins two sequences
- Closures can now be marked @noescape
- Classes can now have static methods and properties
- Constants no longer require immediate initialization
- A new Set data structure
- Implicit bridging has been reduced
- Multiple if let bindings
- Typecasting now includes as!
Download all Swift 1.2 changes as a playground Link to Swift 1.2 changes
