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We’ve been able to watch Swift 3 materialize through the Swift Evolution mailing list throughout the year, and with WWDC 2016 behind us, we have a pretty clear picture of what Swift 3 will be.

Today we’ll start taking a look at what’s new and changed in this release, and how it can help us build our apps. First up is the “Great , Let’s begin.

It all started with this proposal on Swift Evolution:
“Better Translation of Objective-C APIs into Swift”.

When Swift was first announced, one of the huge selling points was how we could use the same APIs we were already familiar with.

Unfortunately, this meant a lot of Objective-C baggage found its way into the Swift code we were writing.

Swift 3 aims to fix this by improving the way Swift imports Objective-C code.

Take this Swift 2 code:

path.addLineToPoint(somePoint)

The function is imported with a definition like this:

func addLineToPoint(_: CGPoint)

In Swift 3, this would instead be imported as:

func addLine(to point: CGPoint)

And we could use it like this:

path.addLine(to: containerTop)

Swift 3 removes the repetitive names of the types, and properly brings in a (now required) argument label for the first parameter.

Additionally, Swift 3 drops the NS prefix from Foundation types, so instead of:

var now = NSDate()

We’ll now be writing:

var now = Date()

Many Foundation types also now get proper Swift let/var mutability semantics:

var now = Date()
now.addTimeInterval(60) // works

let now = Date()
now.addTimeInterval(60) // compiler error

Swift 3 also prepends the word ‘is’ to imported Objective-C Boolean properties, and converts enums to be lowercased:

path.isEmpty // was just path.empty in Swift 2
var formatter = NumberFormatter()
formatter.numberStyle = .spellOut

That’s all for now, next we’ll continue looking at more Swift 3 changes and enhancements.



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