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

// TODO:

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)
  • @dynamicCallable参数
    • 无参数标签withArguments,你可以使用任何遵循ExpressibleByArrayLiteral的类型,例如 数组,数组切片,set等
    • 有参数标签的withKeywordArguments,使用任何遵循ExpressibleByDictionaryLiteral的类型,例如,字典,和key value 对,更多KeyValuePairs可以的看这里,什么是KeyValuePairs?
  • 你可以将其用在结构体,枚举,类和协议上
  • 如果你使用withKeywordArguments而不是withArguments,你仍然按照无参数标签的方式使用,只是key是空字符串。
  • 如果withKeywordArguments或者withArguments标记为抛出错误,调用类型也会抛出错误。
  • 不能在扩展中使用@dynamicCallable
  • 你仍然可以添加属性和方法。

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

  • #warning,警告,主要为了提示后续需要处理,Xcode可以编译通过
  • #error, 常用在Library中,强制提示,需要修复,否则不会编译通过。
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。

  • filter返回的是个字典
  • map 返回的仍然是数组
  • mapValues,返回的则是字典
  • grouping初始化方法,可以将数组处理成字典
  • default赋值和取值会比较方便。
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

  • prefix(while:): 遍历所有元素,直到遇到不满足条件的元素 ,并且返回满足的元素
  • drop(while:): 就是返回 prefix(while:)相反的就好。
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]https://swift.org/documentation/api-design-guidelines/)方法的部分是:

  • 按照它们的副作用来命名函数和方法
    • 无副作用的按照名次来命名。x.distance(to: y)i.successor()
    • 有副作用的按照动词来命名。print(x)x.sort()x.append(y)
    • 有修改和无修改命名
      • 动词的方法中,无修改的使用过去时ed(通常是,不修改原数据,而是返回新的),有修改的使用现在时ing
      • 名词的方法中,无修改的使用名词,有修改的前面加上from

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