Swift 2.3-> 3.0

時間 2019-11-08

標籤 swift 2.3 3.0 欄目 Swift 简体版

原文原文鏈接

是否從Swift2.3升級到3.0呢？git

若是你有一個意義很是重大的Swift編碼庫（就像咱們在VTS中作的同樣），那麼別猶豫了，趕快更新吧。另外爲了項目的須要，Xcode的更新，跟隨蘋果的步伐，最新的技術，仍是麻溜的跟上把。github

可是若是你的Swift代碼不是很是的繁重，那麼你就直接忽略2.3吧。objective-c

下面有一些事情須要記住：swift

1.依賴庫很是重要，確保你的依賴庫支持2.3仍是3.0-大多數的lib/framework是二者都支持的（Alamofire,Charts）.然而升級到3.0是你的惟一途徑。新的發展將會在Swift3.0展開。全部的swift2.3版本的相關依賴庫將會被凍結，也就是不在更新。閉包

2.Xcode8.x 將會移除對Swift2.3的支持。Swift2.3註定是大型工程的一個過渡品。因此咱們須要努力的升級到swift3.0app

3.若是你有一個私有的CocoaPods用於分享代碼在多個工程中，那麼你不得不立刻更新。dom

固然你能夠只更新到2.3，可是你只能推遲，由於在發佈Xcode9以前你必須移植到Swift3。async

將問題從Swift2.2遷移到2.3ide

這個遷移可能將Range<T>到CountableRange<T>.可是CountableRange<T>只存在於Swift3函數

遷移者將會添加評論 /* 遷移者修復：使用變量類型爲： DispatchSpecificKey*/去使用dispatch_queue_set_specific() 這是惟一將來相關在Swift3遷移中。

將問題從Swift2.x遷移到3.0

Swift3.0是一個打破一切的版本。swift3意味着打破一切而且移除了全部不利於一個語言長期發展的不利因素。這固然也意味着不少的東西被改變了。你也須要去改變這些使你的工程更加兼容。

Swift 2.3

Swift2.3是一個很是小的更新。具體多麼小呢？實際上，這裏僅僅只有一個改變。OC代碼在編譯時爲空的檢查在蘋果的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) {
	…
	}

其餘的變化包括一些小的重命名和一些可選類型的初始化如今返回了他們應該返回的類型而再也不是可選類型。這些應用就想從bundle初始化nib同樣。

Swift3.0

重大的更改（你必須須要注意）

私有的定義已經被更改了，下面來介紹一下fileprivate

之前格式化的私有如今在Swift3.0中變成了fileprivate。一個fileprivate可使用在一個Extension中

可是一個私有private的變量不可使用在一個Extension的類中

// 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)!
}
}