Hipo log

Swift 3到5.1新特性整理

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Intro

Hipo 2.0 重写从Swift 1的版本写到2的版本,后续Hipo功能稳定,更新慢了很多……,Swift本身却在长足的发展,5.0都已经发布了,本文对Swift 3.0 到Swift 5.1 的更新点做个总结。

为了方便阅读,准备从新到旧的总结。

下面所有的东西,都是来自hackingwithswift.com


Swift 5.1

Swift 5.1的更新比较迟,单独成篇Swift 5.1的变化

Swift 5.0

Swift 5.0 最重要的自然是ABI Stability, 对此可以看这篇 Swift ABI 稳定对我们到底意味着什么

当然还有其他的更新。

Result类型

SE-0235提议的实现。用来在复杂对象中的错误处理。

Result类型有两个带泛型的枚举成员successfailure,而且failure的泛型必须遵循Swift的Error类型。

常规的使用

enum NetworkError: Error { case badURL } import Foundation func fetchUnreadCount1(from urlString: String, completionHandler: @escaping (Result<Int, NetworkError>) -> Void) { guard let url = URL(string: urlString) else { completionHandler(.failure(.badURL)) return } // complicated networking code here print("Fetching \(url.absoluteString)...") completionHandler(.success(5)) } fetchUnreadCount1(from: "https://www.hackingwithswift.com") { result in switch result { case .success(let count): print("\(count) unread messages.") case .failure(let error): print(error.localizedDescription) } }

首先,Result有个get()方法,要么返回成功值,要么抛出错误。那么可以这么使用。

fetchUnreadCount1(from: "https://www.hackingwithswift.com") { result in if let count = try? result.get() { print("\(count) unread messages.") } }

再次,Result可以接受一个闭包来初始化,如果闭包成功返回,就会把它放到success的一边,如果抛出错误,就放到failure的一边。

let result = Result { try String(contentsOfFile: someFile) }

最后,你可以使用你自己的错误枚举,但是Swift官方建议,你说用Swift.Error来作为Error的参数。

“it’s expected that most uses of Result will use Swift.Error as the Error type argument.”

Raw string

SE-0200 引入了,使用#来包裹的Raw字符串,里面的字符不会做处理,特别是一些转义字符。

差值需要这样做

let answer = 42 let dontpanic = #"The answer to life, the universe, and everything is \#(answer)."#

这个对于正则的特别好用

let regex1 = "\\\\[A-Z]+[A-Za-z]+\\.[a-z]+" let regex2 = #"\\[A-Z]+[A-Za-z]+\.[a-z]+"#

自定义字符串插值

SE-0228提案改进了Swift的字符串插值,让其更高效和自由。

struct User { var name: String var age: Int } extension String.StringInterpolation { mutating func appendInterpolation(_ value: User) { appendInterpolation("My name is \(value.name) and I'm \(value.age)") } } let user = User(name: "Guybrush Threepwood", age: 33) print("User details: \(user)") // User details: My name is Guybrush Threepwood and I'm 33,

// TODO: 更多使用,需要多研究

动态可调用类型

SE-0216 增加了@dynamicCallable属性,来支持方法的动态调用,类似@dynamicMemberLookup

你可以将

struct RandomNumberGenerator { func generate(numberOfZeroes: Int) -> Double { let maximum = pow(10, Double(numberOfZeroes)) return Double.random(in: 0...maximum) } }

转变为

@dynamicCallable struct RandomNumberGenerator { func dynamicallyCall(withKeywordArguments args: KeyValuePairs<String, Int>) -> Double { let numberOfZeroes = Double(args.first?.value ?? 0) let maximum = pow(10, numberOfZeroes) return Double.random(in: 0...maximum) } } let random = RandomNumberGenerator() let result = random(numberOfZeroes: 0)

处理未来的枚举值

SE_0192的实现。

有时候枚举的switch中使用default来防治出错,但不会真正的使用,但是如果未来加了新的case,那些处理地方就会遗漏。现在可以添加@unknkow来出触发Xcode的提示。

func showNew(error: PasswordError) { switch error { case .short: print("Your password was too short.") case .obvious: print("Your password was too obvious.") @unknown default: print("Your password wasn't suitable.") } }

这样,如果如果代码中,没有处理干净PasswordError (switch block is no longer exhaustive),就会告警.

try?抹平嵌套可选

struct User { var id: Int init?(id: Int) { if id < 1 { return nil } self.id = id } func getMessages() throws -> String { // complicated code here return "No messages" } } let user = User(id: 1) let messages = try? user?.getMessages()

上面的例子中,Swift 4.2以及之前的,message会是 String??, 这样就不太合理,Swift 5中,就能返回抹平的String?

检查整数是否为偶数

SE-0225添加了, isMultiple(of:)来检查整数是否为偶数, 和if rowNumber % 2 == 0效果一样。

let rowNumber = 4 if rowNumber.isMultiple(of: 2) { print("Even") } else { print("Odd") }

字典compactMapValues()方法

SE-0218,为字典添加了compactMapValues()方法,这个就像结合了,数组compactMap()方法(遍历成员,判断可选的值,然后丢弃nil成员)和字典的mapValues()方法(只转换字典的value)。

let times = [ "Hudson": "38", "Clarke": "42", "Robinson": "35", "Hartis": "DNF" ] let finishers1 = times.compactMapValues { Int($0) } let finishers2 = times.compactMapValues(Int.init) let people6 = [ "Paul": 38, "Sophie": 8, "Charlotte": 5, "William": nil ] let knownAges = people6.compactMapValues { $0 } print("compactMapValues, \(finishers1), \(finishers2)\(knownAges)") // compactMapValues, ["Clarke": 42, "Robinson": 35, "Hudson": 38], ["Robinson": 35, "Clarke": 42, "Hudson": 38],["Charlotte": 5, "Sophie": 8, "Paul": 38]

撤回的功能: 带条件的计数

SE-0220, 引入了count(where:)函数,来计算遵循Sequence列表中满足条件成员的个数。

let scores = [100, 80, 85] let passCount = scores.count { $0 >= 85 } let pythons = ["Eric Idle", "Graham Chapman", "John Cleese", "Michael Palin", "Terry Gilliam", "Terry Jones"] let terryCount = pythons.count { $0.hasPrefix("Terry") }

这个功能因为性能问题,被撤回了。


Swift 4.2

CaseIterable协议

SE-0194提议的实现,Swift4.2 增加了CaseIterable协议,能够给枚举的allCases属性自动产生所有的枚举的数组。

enum Pasta: CaseIterable { case cannelloni, fusilli, linguine, tagliatelle } for shape in Pasta.allCases { print("I like eating \(shape).") }

当然还可以自行实现

enum Car: CaseIterable { static var allCases: [Car] { return [.ford, .toyota, .jaguar, .bmw, .porsche(convertible: false), .porsche(convertible: true)] } case ford, toyota, jaguar, bmw case porsche(convertible: Bool) }

警告和错误指令

SE-0196提议的实现。Swift 4.2提供这两个提示,来让Xcode在编译时候作出提示

func encrypt(_ string: String, with password: String) -> String { #warning("This is terrible method of encryption") return password + String(string.reversed()) + password } struct Configuration { var apiKey: String { #error("Please enter your API key below then delete this line.") return "Enter your key here" } }

还可以和#if配合使用。

#if os(macOS) #error("MyLibrary is not supported on macOS.") #endif

动态查找成员

SE-0195提议的实现。Swift 4.2提供了@dynamicMemberLookup的属性,和subscript(dynamicMember:)陪着使用,实现动态的属性的取值。

@dynamicMemberLookup struct Person5 { subscript(dynamicMember member: String) -> String { let properties = ["name": "Tylor Swift", "city" : "Nashville"] return properties[member, default: ""] } } let person5 = Person5() print("person5.name: \(person5.name)") print("person5.city: \(person5.city)") print("person5.favoriteIceCream: \(person5.favoriteIceCream)") // person5.name: Tylor Swift // person5.city: Nashville // person5.favoriteIceCream:

当然也有类似多态的用法。

@dynamicMemberLookup struct Person5 { subscript(dynamicMember member: String) -> String { let properties = ["name": "Tylor Swift", "city" : "Nashville"] return properties[member, default: ""] } subscript(dynamicMember member: String) -> Int { let properties = ["age": 26, "height": 178] return properties[member, default: 0] } } let person5 = Person5() print("person5.age: \(person5.age)") let age: Int = person5.age print("person5.age2: \(age)") // person5.age: // person5.age2: 26

注意你需要指定明确指定类型,Swift才能正确使用。

而且如果已经有存在属性,动态属性将不会生效

struct Singer { public var name = "Justin Bieber" subscript(dynamicMember member: String) -> String { return "Taylor Swift" } } let singer = Singer() print(singer.name) // Justin Bieber

@dynamicMemberLookup可以用在协议,结构体,枚举,类,甚至标注为@objc的类,以及它们的继承者。

例如,陪着协议的使用,你可以这样用

@dynamicMemberLookup protocol Subscripting { } extension Subscripting { subscript(dynamicMember member: String) -> String { return "This is coming from the subscript" } } extension String: Subscripting { } let str = "Hello, Swift" print(str.username)

Chris Lattner提议中的例子很有意义,

@dynamicMemberLookup enum JSON { case intValue(Int) case stringValue(String) case arrayValue(Array<JSON>) case dictionaryValue(Dictionary<String, JSON>) var stringValue: String? { if case .stringValue(let str) = self { return str } return nil } subscript(index: Int) -> JSON? { if case .arrayValue(let arr) = self { return index < arr.count ? arr[index] : nil } return nil } subscript(key: String) -> JSON? { if case .dictionaryValue(let dict) = self { return dict[key] } return nil } subscript(dynamicMember member: String) -> JSON? { if case .dictionaryValue(let dict) = self { return dict[member] } return nil } }

正常使用

let json = JSON.stringValue("Example") json[0]?["name"]?["first"]?.stringValue

如果用上述的写法

json[0]?.name?.first?.stringValue

有条件地遵循协议的增强

Swift 4.1引入了有条件地遵循协议

extension Array: Purchaseable where Element: Purchaseable { func buy() { for item in self { item.buy() } } }

但是在Swift 4.1中,如果你要确定对象是否遵循某个协议,会报错。Swift 4.2 修复了这个问题

let items: Any = [Book(), Book(), Book()] if let books = items as? Purchaseable { books.buy() }

还有,Swift 内置的类型,可选,数组,字典,区间,如果它们的成员遵循Hashable,那么它们也会自动遵循Hashable

随机数产生和shuffling

SE-0202提议的实现。Swift 4.2提供了原生的随机数方法。意味着你不需要使用arc4random_uniform()或者GameplayKit来实现了。

let randomInt = Int.random(in: 1..<5) let randomFloat = Float.random(in: 1..<10) let randomDouble = Double.random(in: 1...100) let randomCGFloat = CGFloat.random(in: 1...1000) let randomBool = Bool.random()

SE-0202同样还提议了shuffle()shuffled()

var albums = ["Red", "1989", "Reputation"] // shuffle in place albums.shuffle() // get a shuffled array back let shuffled = albums.shuffled()

还有randomElement()方法。

if let random = albums.randomElement() { print("The random album is \(random).") }

更简单,安全的Hash

SE-0206的实现,让你更简单的为自建类型使用Hashable协议。

Swift 4.1 能够为遵循Hashable协议的类型自动生成hash值。但是如果你需要自行实现仍然需要写不少代码。

Swift 4.2 引入了Hasher结构,提供了随机种子,和通用的hash函数来简化过程

struct iPad: Hashable { var serialNumber: String var capacity: Int func hash(into hasher: inout Hasher) { hasher.combine(serialNumber) } } let first = iPad(serialNumber: "12345", capacity: 256) let second = iPad(serialNumber: "54321", capacity: 512) var hasher = Hasher() hasher.combine(first) hasher.combine(second) let hash = hasher.finalize()

检查列表是否满足条件

SE-0207的实现,提供了allSatisfy()方法来检测数组中所有的元素是否都满足条件。

let scores = [85, 88, 95, 92] let passed = scores.allSatisfy { $0 >= 85 }

原地字典的元素移除

SE-0197提供一个全新的removeAll(where:)方法,以此来提供一个更高效,会操作原数据的类似filter的方法。

var pythons = ["John", "Michael", "Graham", "Terry", "Eric", "Terry"] pythons.removeAll { $0.hasPrefix("Terry") } print(pythons)

Boolean toggling

SE-0199提供了,对Booltoggle()方法,类似

extension Bool { mutating func toggle() { self = !self } }

Swift 4.2 你可以这样

var loggedIn = false loggedIn.toggle()

Swift 4.1

EquatableHashable协议

类和结构体做可比较,需要自己手动实现。

struct Person: Equatable { var firstName: String var lastName: String var age: Int var city: String static func ==(lhs: Person, rhs: Person) -> Bool { return lhs.firstName == rhs.firstName && lhs.lastName == rhs.lastName && lhs.age == rhs.age && lhs.city == rhs.city } } let person1 = Person(firstName: "hicc", lastName: "w", age: 20, city: "shenzhen") let person2 = Person(firstName: "hicc", lastName: "w", age: 20, city: "shenzhen") print("person1 1 == person2 : \(person1 == person2)") // person1 1 == person2 : true

Swift 4.1 提供了Equatable的协议,它会自动的生成==方法。

当然你还是可以自己实现==方法(例如,业务有id之类的属性)。

还有之前实现一个对象的hash值也是一件麻烦的事情,你可能需要手动实现类似:

var hashValue: Int { return firstName.hashValue ^ lastName.hashValue &* 16777619 }

Swift 4.1 提供了Hashable的协议,可以自动生成hashValue,你也还是可以自行实现。

struct Person2: Equatable, Hashable { var firstName: String var lastName: String var age: Int var city: String } let person11 = Person2(firstName: "hicc", lastName: "w", age: 20, city: "shenzhen") let person22 = Person2(firstName: "hicc", lastName: "w", age: 20, city: "shenzhen") print("person11 1 == person22 : \(person11 == person22), \(person11.hashValue)") // person11 1 == person22 : true, 5419288582170212869

Codable协议,Key值转化策略

Swift 4提供了很方便的Codable协议,但是它使用下划线snake_case而不是驼峰式的方式来转化Key,不太自由。

Swift 4.1 中针对这种情况,提供了keyDecodingStrategy,以及keyEncodingStrategy属性(默认.useDefaultKeys)来解决这些问题。

let decoder = JSONDecoder() decoder.keyDecodingStrategy = .convertFromSnakeCase do { let macs = try decoder.decode([Mac].self, from: jsonData) print(macs) } catch { print(error.localizedDescription) } let encoder = JSONEncoder() encoder.keyEncodingStrategy = .convertToSnakeCase let encoded = try encoder.encode(someObject)

有条件地遵循协议

Swift 4.1 实现了SE-0143的提议,容许你类型在某下情况下才遵循某个协议。

extension Array: Purchaseable where Element: Purchaseable { func buy() { for item in self { item.buy() } } }

这样会让你的代码,更加的安全。如下代码Swift中会拒绝编译,因为其未遵循Coodable协议.

import Foundation struct Person { var name = "Taylor" } var people = [Person()] var encoder = JSONEncoder() try encoder.encode(people)

关联类型中的递归限制

Swift 4.1实现了SE-0157提议,在递归协议中,关联类型可以被定义它的协议所限制。

protocol Employee { associatedtype Manager: Employee var manager: Manager? { get set } }

// TODO: 现在感受不太清楚,后续有深入了解在补充。

canImport函数

SE-0075提议的实现。Swift 4.1引入了canImport函数,让你可以检查某个模块能否被导入。

#if canImport(SpriteKit) // this will be true for iOS, macOS, tvOS, and watchOS #else // this will be true for other platforms, such as Linux #endif

之前还有类似的方法

#if !os(Linux) // Matches macOS, iOS, watchOS, tvOS, and any other future platforms #endif #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS) // Matches only Apple platforms, but needs to be kept up to date as new platforms are added #endif

targetEnvironment函数

SE-0190提议的实现,Swift 4.1 提供了targetEnvironment函数,来检测是模拟器还是真实的硬件。

#if targetEnvironment(simulator) // code for the simulator here #else // code for real devices here #endif

flatMap改名为compactMap

flatMap之前一个很有用的作用是能够过滤数组中为nil的元素,Swift 4.2重命名为指意明确,更强大的compactMap

let array = ["1", "2", "Fish"] let numbers = array.compactMap { Int($0) } // [1, 2]

Swift 4.0

Coodable协议

Swift 4之前使用NSCoding来做encoding和decoding的事情,但是需要一些模版代码,也容易出错,Swift 4中 Coodable协议就是为这个而存在。

使用起来简单到不可思议。

struct Language: Codable { var name: String var version: Int } let swift = Language(name: "Swift", version: 4)

完整的使用

let encoder = JSONEncoder() if let encoded = try? encoder.encode(swift) { if let json = String(data: encoded, encoding: .utf8) { print("swift strng\(json)") } let decoder = JSONDecoder() if let decoded = try? decoder.decode(Language.self, from: encoded) { print("Swift name: \(decoded.name)") } }

多行字符串字面量

跨越多行的字符串可以使用"""来包裹。

let quotation = """ The White Rabbit put on his spectacles. "Where shall I begin, please your Majesty?" he asked. "Begin at the beginning," the King said gravely, "and go on till you come to the end; then stop." """

改进Key-value编码中的keypaths

keypaths是指对属性的引用而不去真正读取属性的值。

struct Crew { var name: String var rank: String } struct Starship { var name: String var maxWarp: Double var captain: Crew } let janeway = Crew(name: "Kathryn Janeway", rank: "Captain") let voyager = Starship(name: "Voyager", maxWarp: 9.975, captain: janeway) let nameKeyPath = \Starship.name let maxWarpKeyPath = \Starship.maxWarp let captainName = \Starship.captain.name let starshipName = voyager[keyPath: nameKeyPath] let starshipMaxWarp = voyager[keyPath: maxWarpKeyPath] let starshipCaptain = voyager[keyPath: captainName] print("starshipName \(starshipName),\(starshipCaptain)") // starshipName Voyager, Kathryn Janeway

改进字典函数

Swift 4改进了字典的诸多函数。

let cities = ["Shanghai": 24_256_800, "Karachi": 23_500_000, "Beijing": 21_516_000, "Seoul": 9_995_000]; let massiveCities = cities.filter { $0.value > 10_000_000 } let populations = cities.map { $0.value * 2 } let roundedCities = cities.mapValues { "\($0 / 1_000_000) million people" } let groupedCities = Dictionary(grouping: cities.keys) { $0.first! } let groupedCities2 = Dictionary(grouping: cities.keys) { $0.count } var favoriteTVShows = ["Red Dwarf", "Blackadder", "Fawlty Towers", "Red Dwarf"] var favoriteCounts = [String: Int]() for show in favoriteTVShows { favoriteCounts[show, default: 0] += 1 } print("dic\(massiveCities),\n\(populations),\n\(roundedCities),\n\(groupedCities),\n\(groupedCities2),\n\(favoriteCounts)") // dic["Shanghai": 24256800, "Beijing": 21516000, "Karachi": 23500000], // [43032000, 47000000, 19990000, 48513600], ///["Beijing": "21 million people", "Karachi": "23 million people", "Seoul": "9 million people", "Shanghai": "24 million people"], // ["S": ["Seoul", "Shanghai"], "B": ["Beijing"], "K": ["Karachi"]], // [8: ["Shanghai"], 5: ["Seoul"], 7: ["Beijing", "Karachi"]], // ["Blackadder": 1, "Fawlty Towers": 1, "Red Dwarf": 2]

字符串又变成了Collection类型

字符串是Collection类型,这样就有了诸多便利的方法。

let quote = "It is a truth universally acknowledged that new Swift versions bring new features." let reversed = quote.reversed() for letter in quote { print(letter) }

单侧区间

Swift 4 支持了单侧区间, 缺失的一边为0或者为集合的尽头

let characters = ["Dr Horrible", "Captain Hammer", "Penny", "Bad Horse", "Moist"] let bigParts = characters[..<3] let smallParts = characters[3...] print(bigParts) print(smallParts) // ["Dr Horrible", "Captain Hammer", "Penny"] // ["Bad Horse", "Moist"]

Swift 3.1

扩展限制的优化

Swift支持对扩展做限制。

extension Collection where Iterator.Element: Comparable { func lessThanFirst() -> [Iterator.Element] { guard let first = self.first else { return [] } return self.filter { $0 < first } } } let items = [5, 6, 10, 4, 110, 3].lessThanFirst() print(items)
extension Array where Element: Comparable { func lessThanFirst() -> [Element] { guard let first = self.first else { return [] } return self.filter { $0 < first } } } let items = [5, 6, 10, 4, 110, 3].lessThanFirst() print(items)

上述3.0的对扩展的限制都是通过协议实现。Swift 3.1 支持使用类型来限制。

extension Array where Element == Int { func lessThanFirst() -> [Int] { guard let first = self.first else { return [] } return self.filter { $0 < first } } } let items = [5, 6, 10, 4, 110, 3].lessThanFirst() print(items)

嵌套类型支持泛型

Swift 3.1支持了嵌套类型中使用泛型。

struct Message<T> { struct Attachment { var contents: T } var title: T var attachment: Attachment }

序列(Sequences)协议增加了prefix(while:), drop(while:)两个方法

let names = ["Michael Jackson", "Michael Jordan", "Michael Caine", "Taylor Swift", "Adele Adkins", "Michael Douglas"] let prefixed = names.prefix { $0.hasPrefix("Michael") } print(prefixed) let dropped = names.drop { $0.hasPrefix("Michael") } print(dropped)

Swift 3.0

函数调用必须使用参数标签

Swift特点是函数可以分别制定参数标签(argument label)和参数名称(parameter name)

func someFunction(argumentLabel parameterName: Int) { } // 使用必须带上参数标签 someFunction(argumentLabel: 1) // 如果不指定,参数名称可以作为菜参数标签 func someFunction(firstParameterName: Int, secondParameterName: Int) { } someFunction(firstParameterName: 1, secondParameterName: 2)

如果你不想使用参数标签,可以使用_代替

func someFunction(_ firstParameterName: Int, secondParameterName: Int) { } someFunction(1, secondParameterName: 2)

移除多余代码

主要是一些内置对象,以及和平台相关的精简,让代码更加易读。

// Swift 2.2 let blue = UIColor.blueColor() let min = numbers.minElement() attributedString.appendAttributedString(anotherString) names.insert("Jane", atIndex: 0) UIDevice.currentDevice() // Swift 3 let blue = UIColor.blue let min = numbers.min() attributedString.append(anotherString) names.insert("Jane", at: 0) UIDevice.current

以及

// 第一行是Swift 2.2 // 迪尔汗是Swift 3 " Hello ".stringByTrimmingCharactersInSet(.whitespaceAndNewlineCharacterSet()) " Hello ".trimmingCharacters(in: .whitespacesAndNewlines) "Taylor".containsString("ayl") "Taylor".contains("ayl") "1,2,3,4,5".componentsSeparatedByString(",") "1,2,3,4,5".components(separatedBy: ",") myPath.stringByAppendingPathComponent("file.txt") myPath.appendingPathComponent("file.txt") "Hello, world".stringByReplacingOccurrencesOfString("Hello", withString: "Goodbye") "Hello, world".replacingOccurrences(of: "Hello", with: "Goodbye") "Hello, world".substringFromIndex(7) "Hello, world".substring(from: 7) "Hello, world".capitalizedString "Hello, world".capitalized

以及, lowercaseString -> lowercased()uppercaseString ->uppercased()

dismissViewControllerAnimated(true, completion: nil) dismiss(animated: true, completion: nil) dismiss(animated: true) prepareForSegue() override func prepare(for segue: UIStoryboardSegue, sender: AnyObject?)

枚举和属性从大驼峰替换为小驼峰

正如标题说的,一方面这是Swift推荐的用法,另外就是内置对象的变化

UIInterfaceOrientationMask.Portrait // old UIInterfaceOrientationMask.portrait // new NSTextAlignment.Left // old NSTextAlignment.left // new SKBlendMode.Replace // old SKBlendMode.replace // new

还有就是Swift可选类型是通过枚举来实现的

enum Optional { case None case Some(Wrapped) }

如果使用.Some来处理可选,也需要更改

for case let .some(datum) in data { print(datum) } for case let datum? in data { print(datum) }

更swift地改进C函数

大体来说就是让C函数使用更加的Swift

// Swift 2.2 let ctx = UIGraphicsGetCurrentContext() let rectangle = CGRect(x: 0, y: 0, width: 512, height: 512) CGContextSetFillColorWithColor(ctx, UIColor.redColor().CGColor) CGContextSetStrokeColorWithColor(ctx, UIColor.blackColor().CGColor) CGContextSetLineWidth(ctx, 10) CGContextAddRect(ctx, rectangle) CGContextDrawPath(ctx, .FillStroke) UIGraphicsEndImageContext() // Swift 3 if let ctx = UIGraphicsGetCurrentContext() { let rectangle = CGRect(x: 0, y: 0, width: 512, height: 512) ctx.setFillColor(UIColor.red.cgColor) ctx.setStrokeColor(UIColor.black.cgColor) ctx.setLineWidth(10) ctx.addRect(rectangle) ctx.drawPath(using: .fillStroke) UIGraphicsEndImageContext() }

以及

// 第一行是Swift 2.2 // 第二行是Swift 3 CGAffineTransformIdentity CGAffineTransform.identity CGAffineTransformMakeScale(2, 2) CGAffineTransform(scaleX: 2, y: 2) CGAffineTransformMakeTranslation(128, 128) CGAffineTransform(translationX: 128, y: 128) CGAffineTransformMakeRotation(CGFloat(M_PI)) CGAffineTransform(rotationAngle: CGFloat(M_PI))

名次和动词

这部分属于Swift更加语义化的改进,到现在5.1的时候一直在改进,目前官网最近的规范Swift.org - API Design Guidelines方法的部分是:

-----2019-05-25---9.33.04

-----2019-05-25---9.33.22