Swift 2.3-> 3.0

时间 2019-11-08

标签 swift 2.3 3.0 栏目 Swift 繁體版

原文原文链接

是否从Swift2.3升级到3.0呢？git

若是你有一个意义很是重大的Swift编码库（就像咱们在VTS中作的同样），那么别犹豫了，赶快更新吧。另外为了项目的须要，Xcode的更新，跟随苹果的步伐，最新的技术，仍是麻溜的跟上把。github

可是若是你的Swift代码不是很是的繁重，那么你就直接忽略2.3吧。objective-c

下面有一些事情须要记住：swift

1.依赖库很是重要，确保你的依赖库支持2.3仍是3.0-大多数的lib/framework是二者都支持的（Alamofire,Charts）.然而升级到3.0是你的惟一途径。新的发展将会在Swift3.0展开。全部的swift2.3版本的相关依赖库将会被冻结，也就是不在更新。闭包

2.Xcode8.x 将会移除对Swift2.3的支持。Swift2.3注定是大型工程的一个过渡品。因此咱们须要努力的升级到swift3.0app

3.若是你有一个私有的CocoaPods用于分享代码在多个工程中，那么你不得不立刻更新。dom

固然你能够只更新到2.3，可是你只能推迟，由于在发布Xcode9以前你必须移植到Swift3。async

将问题从Swift2.2迁移到2.3ide

这个迁移可能将Range<T>到CountableRange<T>.可是CountableRange<T>只存在于Swift3函数

迁移者将会添加评论 /* 迁移者修复：使用变量类型为： DispatchSpecificKey*/去使用dispatch_queue_set_specific() 这是惟一将来相关在Swift3迁移中。

将问题从Swift2.x迁移到3.0

Swift3.0是一个打破一切的版本。swift3意味着打破一切而且移除了全部不利于一个语言长期发展的不利因素。这固然也意味着不少的东西被改变了。你也须要去改变这些使你的工程更加兼容。

Swift 2.3

Swift2.3是一个很是小的更新。具体多么小呢？实际上，这里仅仅只有一个改变。OC代码在编译时为空的检查在苹果的SDK中被更新。

// Swift 2.2
	let image = CIImage(MTLTexture: texture, options: options)
	let extent = image.extent // can crash

	// Swift 3.0
	let image = CIImage(MTLTexture: texture, options: options)!
	// or
	if let image = CIImage(MTLTexture: texture, options: options) {
	…
	}

其余的变化包括一些小的重命名和一些可选类型的初始化如今返回了他们应该返回的类型而再也不是可选类型。这些应用就想从bundle初始化nib同样。

Swift3.0

重大的更改（你必须须要注意）

私有的定义已经被更改了，下面来介绍一下fileprivate

之前格式化的私有如今在Swift3.0中变成了fileprivate。一个fileprivate可使用在一个Extension中

可是一个私有private的变量不可使用在一个Extension的类中

// Before
	var myArray = [ 1 ,3, 2, 5, 4 ]
	myArray.sort() // returns a new sorted version of `myArray`
	myArray.sortInPlace() // sorts in place

	// After
	myArray.sort() // sorts in place
	myArray.sorted() // returns a new sorted version of `myArray`.

//before
	var myDate = Date()
	myDate.addTimeInterval(60) // OK

	//after
	let myOtherDate = Date()
	myOtherDate.addTimeInterval(60) // Error, as expected

	// Before
	let topLeft = bounds.origin
	let bottomRight = CGPoint(x: bounds.size.width, y: bounds.size.height)
	let path = CGPathCreateMutable()
	CGPathMoveToPoint(path, &transform, topLeft.x, topLeft.y)
	CGPathAddLineToPoint(path, &transform, CGRectGetMidX(bounds), bottomRight.y)
	CGPathAddLineToPoint(path, &transform, bottomRight.x, topLeft.y)
	CGPathAddLineToPoint(path, &transform, topLeft.x, topLeft.y)
	CGPathAddLineToPoint(path, &transform, topLeft.x, bottomRight.y)
	CGPathAddLineToPoint(path, &transform, bottomRight.x, bottomRight.y)
	CGPathAddLineToPoint(path, &transform, bottomRight.x, topLeft.y)
	CGContextAddPath(context, path)

	// After
	let topLeft = bounds.origin
	let bottomRight = CGPoint(x: bounds.size.width, y: bounds.size.height)
	let path = CGMutablePath()
	path.move(transform: &transform, x: topLeft.x, y: topLeft.y)
	path.addLine(transform: &transform, x: bounds.midX, y: bottomRight.y)
	path.addLine(transform: &transform, x: bottomRight.x, y: topLeft.y)
	path.addLine(transform: &transform, x: topLeft.x, y: topLeft.y)
	path.addLine(transform: &transform, x: topLeft.x, y: bottomRight.y)
	path.addLine(transform: &transform, x: bottomRight.x, y: bottomRight.y)
	path.addLine(transform: &transform, x: bottomRight.x, y: topLeft.y)
	context.addPath(path)

let path = UIBezierPath()
let point = CGPoint(x: 2, y: 3)
let string = NSString("Hello world!")
// Before
path.moveToPoint(point)
string.characterAtIndex(3)
// After
path.move(to: point)
string.character(at: 3)

// Before
let queue = dispatch_queue_create("com.test.myqueue", nil)
dispatch_async(queue) {
print("Hello World")
}
// After
let queue = DispatchQueue(label: "com.test.myqueue")
queue.asynchronously {
print("Hello World")
}

myIndex.successor() => myCollection.index(after: myIndex)
myIndex.predecessor() => myCollection.index(before: myIndex)
myIndex.advance(by: …) => myCollection.index(myIndex, offsetBy: …)

// before
words.sort(isOrderedBefore: >)
let sum = measurements.reduce(0, combine: +)

// after
words.sort(by: >)
let sum = measurements.reduce(0, +)

// Before
infix operator <> { precedence 100 associativity left }

// After
precedencegroup ComparisonPrecedence {
associativity: left
higherThan: LogicalConjunctionPrecedence
}
infix operator <> : ComparisonPrecedence

// Before
// HealthKit has the following strings:
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyMassIndex;
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyFatPercentage;
HK_EXTERN NSString * const HKQuantityTypeIdentifierHeight;
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyMass;
HK_EXTERN NSString * const HKQuantityTypeIdentifierLeanBodyMass;
// They were previously imported as swift Strings

// After
// Instead of importing this as a string, Swift will import this like so:
enum HKQuantityTypeIdentifier : String {
case BodyMassIndex
case BodyFatPercentage
case Height
case BodyMass
case LeanBodyMass
}

// Before
catch let error as AVError where error == .diskFull {
// AVError is an enum, so one only gets the equivalent of the code.
// There is no way to access the localized description (for example) or
// any other information typically stored in the ``userInfo`` dictionary.
}

// or
catch let error as NSError where error._domain == AVFoundationErrorDomain && error._code == AVFoundationErrorDomain.diskFull.rawValue {
// okay: userInfo is finally accessible, but still weakly typed
}

// And in usage:
catch let error as NSError where error._domain = AVFoundationErrorDomain {
if let time = error.userInfo[AVErrorTimeKey] as? CMTime {
// ...
}
}

// After
catch let error as AVError {
if let time = error.time {
// ...
}
}

// Before:
func curried(x: Int)(y: String) -> Float {
return Float(x) + Float(y)!
}

// After:
func curried(x: Int) -> (String) -> Float {
return {(y: String) -> Float in
return Float(x) + Float(y)!
}
}