三個(gè)協(xié)議

RawRepresentable協(xié)議

public protocol RawRepresentable {
associatedtype RawValue
init?(rawValue: Self.RawValue)
varrawValue: Self.RawValue {get}
}
/// The `RawRepresentable` protocol is seen mainly in two categories of types: enumerations with raw value types and option sets.1偷仿、 For any enumeration with a string, integer, or floating-point raw type, the Swift compiler automatically adds `RawRepresentable` conformance. 
/// enum Counter: Int {
/// case one = 1, two, three, four, five
/// }
/// 2搪花、 Option sets all conform to `RawRepresentable` by inheritance using the `OptionSet` protocol.
// 單獨(dú)使用 RawRepresentable 的情況

struct Goods: RawRepresentable {
  // 使用非可選初始化方法實(shí)現(xiàn)協(xié)議可選的初始化方法要求
  init(rawValue: Int) {
    self = Goods()
  }
  var rawValue: Int
  typealias RawValue = Int
  init() {
    self.rawValue = 0
  }
}

SetAlgebra協(xié)議

publicprotocolSetAlgebra : Equatable, ExpressibleByArrayLiteral {
/// A type for which the conforming type provides a containment test.
/// associatedtypeElement
init()
funccontains(_member: Self.Element) -> Bool
funcunion(_other: Self) -> Self
funcintersection(_other: Self) -> Self
funcsymmetricDifference(_other: Self) -> Self
mutatingfuncinsert(_newMember: Self.Element) -> (inserted: Bool, memberAfterInsert: Self.Element)
mutatingfuncremove(_member: Self.Element) -> Self.Element?
mutatingfuncupdate(with newMember: Self.Element) -> Self.Element?
mutatingfuncformUnion(_other: Self)
mutatingfuncformIntersection(_other: Self)
mutatingfuncformSymmetricDifference(_other: Self)
    ......

OptionSet協(xié)議

publicprotocolOptionSet : RawRepresentable, SetAlgebra {
associatedtypeElement = Self
init(rawValue: Self.RawValue)
}

// OptionSet等價(jià)寫法

publicprotocolOptionSet : SetAlgebra {
associatedtypeElement = Self
init(rawValue: Self.RawValue)
  associatedtypeRawValue
//init?(rawValue: Self.RawValue) // 非可選初始化方法可涵蓋此方法
varrawValue: Self.RawValue {get}
}

OptionSet 定義類型

以結(jié)構(gòu)體類型為例令杈，MusicSets 如下：

structMusicSets: OptionSet {
//typealiasElement = Self
typealiasRawValue = Int
varrawValue: Int
init(rawValue: Int) {
self.rawValue = rawValue
  }
}

// 注意： MusicSets 對(duì) SetAlgebra協(xié)議的實(shí)現(xiàn) 默認(rèn)由OptionSet Extension咱娶，見下文“OptionSet 的 Extension分析”
// 簡(jiǎn)化版
structMusicSets: OptionSet {
varrawValue: Int
// 編譯器自動(dòng)推導(dǎo)
//  typealias RawValue = Int
init(rawValue: Int) {
self.rawValue = rawValue
  }
}

// 精簡(jiǎn)版
structMusicSets: OptionSet {
varrawValue: Int
// 編譯器自動(dòng)推導(dǎo)
//  typealias RawValue = Int
// 編譯器自動(dòng)生成（包含所有需要初始化的 成員變量, rawValue）
//  init(rawValue: Int) {
//    self.rawValue = rawValue
//  }
}

// 或者
structMusicSets: OptionSet {
//  var rawValue: Int
letrawValue: Int
}

加上類屬性，如下是一個(gè)通常的OptionSet寫法

structMusicSets: OptionSet {
//  var rawValue: Int
letrawValue: Int
  // 0001
  // 0010
  // 0100
  // 1000
  // 0111
staticletclassic = MusicSets(rawValue: 1 << 0)
staticletcountry = MusicSets(rawValue: 1 << 1)
staticletrock = MusicSets(rawValue: 1 << 2)
staticletpop = MusicSets(rawValue: 1 << 3)
staticletmix = MusicSets(rawValue: 7)
}

OptionSet 使用

OptionSet 在Swift當(dāng)中 填補(bǔ)了Enum中缺少的 bitmask 位選集合的功能

functest() {
  let sets1 = MusicSets.classic
  let sets2 = MusicSets.country
  let sets3 = MusicSets.rock
  let sets4 = MusicSets.pop
  let music = MusicSets.mix
  print("Mix contains1: ", music.contains(sets1))
  print("Mix contains2: ", music.contains(sets2))
  print("Mix contains3: ", music.contains(sets3))
  print("Mix contains4: ", music.contains(sets4))

  let music2: MusicSets = [sets1, sets2, sets3]
  print("Set contains1: ", music2.contains(sets1))
  print("Set contains2: ", music2.contains(sets2))
  print("Set contains3: ", music2.contains(sets3))
  print("Set contains4: ", music2.contains(sets4))
  print("Set rawValue: ", music2.rawValue)
  }

OptionSet 的 Extension 分析

OptionSet 的 rawValue秉颗？ 可以 定義String類型嗎巨朦？

Error: Type 'MusicSets2' does not conform to protocol 'SetAlgebra'
structMusicSets2: OptionSet {
    //    var rawValue: Int
letrawValue: String
//    init?(rawValue: String) {
//        <#code#>
//    }

//    init() {
//        <#code#>
//    }

//    mutating func formUnion(_ other: __owned MusicSets) {
//        <#code#>
//    }

//    mutating func formIntersection(_ other: MusicSets) {
//        <#code#>
//    }

//    mutating func formSymmetricDifference(_ other: __owned MusicSets) {
//        <#code#>
//    }
}

rawValue 改成 String 之后，就出現(xiàn)編譯錯(cuò)誤：類型'MusicSets2' 未遵守 SetAlgebra協(xié)議赶撰，很有可能一些默認(rèn)的實(shí)現(xiàn)被磨掉了舌镶。下面從 OptionSet 的擴(kuò)展中去查找答案(optionSet 有若干個(gè)擴(kuò)展，默認(rèn)實(shí)現(xiàn)了很多功能豪娜，詳情請(qǐng)參考官網(wǎng)文檔)餐胀。

Extension: 1 通用實(shí)現(xiàn)

/// `OptionSet` requirements for which default implementations
/// are supplied.
extensionOptionSet {
@inlinablepublicfuncunion(_other: Self) -> Self
@inlinablepublicfuncintersection(_other: Self) -> Self
@inlinablepublicfuncsymmetricDifference(_other: Self) -> Self
}

Extension: 2 Where 條件實(shí)現(xiàn)

/// `OptionSet` requirements for which default implementations are
/// supplied when `Element == Self`, which is the default.
extensionOptionSetwhereSelf == Self.Element {
@inlinablepublicfunccontains(_member: Self) -> Bool
@inlinablepublicmutatingfuncinsert(_newMember: Self.Element) -> (inserted: Bool, memberAfterInsert: Self.Element)
@inlinablepublicmutatingfuncremove(_member: Self.Element) -> Self.Element?
@inlinablepublicmutatingfuncupdate(with newMember: Self.Element) -> Self.Element?
}

Extension: 3 Where 條件實(shí)現(xiàn)

extensionOptionSetwhereSelf.RawValue : FixedWidthInteger {
@inlinablepublicinit()
@inlinablepublicmutatingfuncformUnion(_other: Self)
@inlinablepublicmutatingfuncformIntersection(_other: Self)
@inlinablepublicmutatingfuncformSymmetricDifference(_other: Self)
}

補(bǔ)充：協(xié)議的關(guān)聯(lián)類型測(cè)試

protocolProtocol0 {
  // 關(guān)聯(lián)類型 沒(méi)有約束、有默認(rèn)值
associatedtypeElement0 =Self
}
protocolProtocol1 {
  // 關(guān)聯(lián)類型有約束
associatedtypeElement1: UIView
}
protocolProtocol2 {
  // 關(guān)聯(lián)類型 沒(méi)有約束瘤载、有默認(rèn)值
associatedtypeElement2 = UIView
}
protocolProtocol3 {
  // 關(guān)聯(lián)類型有約束否灾、有默認(rèn)值
associatedtypeElement3: UIView = UIButton
}
protocolProtocol04 {
  // 關(guān)聯(lián)類型有約束
associatedtypeElement041: UIView
associatedtypeElement042: UIView
}
protocolProtocol4: Protocol04 {
  // 關(guān)聯(lián)類型有約束、有默認(rèn)值
associatedtypeElement041 = UIResponder
associatedtypeElement042 = UIButton
associatedtypeElement4: UIView = UIButton
}

structMusic: Protocol0, Protocol1, Protocol2, Protocol3, Protocol4 {
  // 必須指定類型
typealiasElement1 = UIButton
  // 有默認(rèn)值鸣奔，可以不指定類型墨技，也可以改變指向
typealiasElement0 = NSObject
typealiasElement2 = NSObject
//  typealias Element3 = NSObject
typealiasElement3 = UIButton
typealiasElement4 = UIButton
  // Element041 有: UIView約束，因此 Protocol4中 對(duì) Element041 的指定（成為Music的默認(rèn)指定）不符合約束要求挎狸，需要重新指定
typealiasElement041 = UIButton
}