如何在Swift中创建NS_OPTIONS样式的位掩码枚举？

Question

在Apple有关与C API交互的文档中，他们描述了将NS_ENUM标记的C样式枚举作为Swift枚举导入的方式。这是有道理的，并且由于Swift中的枚举很容易作为enum值类型提供，因此很容易看到如何创建我们自己的枚举。

再往下，它说了关于NS_OPTIONS标记C样式的选项：

Swift还会导入标有NS_OPTIONS宏的选项。而选项的行为类似于进口枚举，选项还可以支持一些位操作，如&，|和~。在Objective-C中，您表示一个常量为零（0）的空选项集。在Swift中，用于nil表示没有任何选项。

鉴于optionsSwift中没有值类型，我们如何创建要使用的C-Style选项变量？

Answer 1

斯威夫特3.0与Swift 2.0几乎相同。OptionSetType重命名为OptionSet，并且按惯例将枚举写为小写。struct MyOptions : OptionSet {&nbsp; &nbsp; let rawValue: Int&nbsp; &nbsp; static let firstOption&nbsp; = MyOptions(rawValue: 1 << 0)&nbsp; &nbsp; static let secondOption = MyOptions(rawValue: 1 << 1)&nbsp; &nbsp; static let thirdOption&nbsp; = MyOptions(rawValue: 1 << 2)}noneSwift 3建议不要提供选项，而只是使用空数组文字：let noOptions: MyOptions = []其他用法：let singleOption = MyOptions.firstOptionlet multipleOptions: MyOptions = [.firstOption, .secondOption]if multipleOptions.contains(.secondOption) {&nbsp; &nbsp; print("multipleOptions has SecondOption")}let allOptions = MyOptions(rawValue: 7)if allOptions.contains(.thirdOption) {&nbsp; &nbsp; print("allOptions has ThirdOption")}斯威夫特2.0在Swift 2.0中，协议扩展会处理大多数样板文件，这些样板文件现在已作为符合的结构导入OptionSetType。（RawOptionSetType自Swift 2 beta 2起已消失。）声明要简单得多：struct MyOptions : OptionSetType {&nbsp; &nbsp; let rawValue: Int&nbsp; &nbsp; static let None&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= MyOptions(rawValue: 0)&nbsp; &nbsp; static let FirstOption&nbsp; = MyOptions(rawValue: 1 << 0)&nbsp; &nbsp; static let SecondOption = MyOptions(rawValue: 1 << 1)&nbsp; &nbsp; static let ThirdOption&nbsp; = MyOptions(rawValue: 1 << 2)}现在我们可以使用基于集合的语义MyOptions：let singleOption = MyOptions.FirstOptionlet multipleOptions: MyOptions = [.FirstOption, .SecondOption]if multipleOptions.contains(.SecondOption) {&nbsp; &nbsp; print("multipleOptions has SecondOption")}let allOptions = MyOptions(rawValue: 7)if allOptions.contains(.ThirdOption) {&nbsp; &nbsp; print("allOptions has ThirdOption")}斯威夫特1.2看着由夫特导入的（Objective-C的选项UIViewAutoresizing，例如），我们可以看到，选项被声明为struct符合协议RawOptionSetType，这反过来又符合&nbsp; _RawOptionSetType，Equatable，RawRepresentable，BitwiseOperationsType，和NilLiteralConvertible。我们可以这样创建自己的：struct MyOptions : RawOptionSetType {&nbsp; &nbsp; typealias RawValue = UInt&nbsp; &nbsp; private var value: UInt = 0&nbsp; &nbsp; init(_ value: UInt) { self.value = value }&nbsp; &nbsp; init(rawValue value: UInt) { self.value = value }&nbsp; &nbsp; init(nilLiteral: ()) { self.value = 0 }&nbsp; &nbsp; static var allZeros: MyOptions { return self(0) }&nbsp; &nbsp; static func fromMask(raw: UInt) -> MyOptions { return self(raw) }&nbsp; &nbsp; var rawValue: UInt { return self.value }&nbsp; &nbsp; static var None: MyOptions { return self(0) }&nbsp; &nbsp; static var FirstOption: MyOptions&nbsp; &nbsp;{ return self(1 << 0) }&nbsp; &nbsp; static var SecondOption: MyOptions&nbsp; { return self(1 << 1) }&nbsp; &nbsp; static var ThirdOption: MyOptions&nbsp; &nbsp;{ return self(1 << 2) }}现在，我们可以像对待MyOptions苹果文档中所述的那样对待这个新的选项集：您可以使用enum-like语法：let opt1 = MyOptions.FirstOptionlet opt2: MyOptions = .SecondOptionlet opt3 = MyOptions(4)而且它的行为也像我们期望的选项那样：let singleOption = MyOptions.FirstOptionlet multipleOptions: MyOptions = singleOption | .SecondOptionif multipleOptions & .SecondOption != nil {&nbsp; &nbsp; &nbsp;// see note&nbsp; &nbsp; println("multipleOptions has SecondOption")}let allOptions = MyOptions.fromMask(7)&nbsp; &nbsp;// aka .fromMask(0b111)if allOptions & .ThirdOption != nil {&nbsp; &nbsp; println("allOptions has ThirdOption")}我已经构建了一个生成器来创建Swift选项集，而无需进行所有查找/替换。最新：对Swift 1.1 beta 3的修改。

Answer 2

Xcode 6.1 Beta 2对RawOptionSetType协议进行了一些更改（请参阅此Airspeedvelocity博客条目和Apple发行说明）。基于Nate Cooks的示例，这里是更新的解决方案。您可以这样定义自己的选项集：struct MyOptions : RawOptionSetType, BooleanType {&nbsp; &nbsp; private var value: UInt&nbsp; &nbsp; init(_ rawValue: UInt) { self.value = rawValue }&nbsp; &nbsp; // MARK: _RawOptionSetType&nbsp; &nbsp; init(rawValue: UInt) { self.value = rawValue }&nbsp; &nbsp; // MARK: NilLiteralConvertible&nbsp; &nbsp; init(nilLiteral: ()) { self.value = 0}&nbsp; &nbsp; // MARK: RawRepresentable&nbsp; &nbsp; var rawValue: UInt { return self.value }&nbsp; &nbsp; // MARK: BooleanType&nbsp; &nbsp; var boolValue: Bool { return self.value != 0 }&nbsp; &nbsp; // MARK: BitwiseOperationsType&nbsp; &nbsp; static var allZeros: MyOptions { return self(0) }&nbsp; &nbsp; // MARK: User defined bit values&nbsp; &nbsp; static var None: MyOptions&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; { return self(0) }&nbsp; &nbsp; static var FirstOption: MyOptions&nbsp; &nbsp;{ return self(1 << 0) }&nbsp; &nbsp; static var SecondOption: MyOptions&nbsp; { return self(1 << 1) }&nbsp; &nbsp; static var ThirdOption: MyOptions&nbsp; &nbsp;{ return self(1 << 2) }&nbsp; &nbsp; static var All: MyOptions&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;{ return self(0b111) }}然后可以像这样使用它来定义变量：let opt1 = MyOptions.FirstOptionlet opt2:MyOptions = .SecondOptionlet opt3 = MyOptions(4)像这样测试位：let singleOption = MyOptions.FirstOptionlet multipleOptions: MyOptions = singleOption | .SecondOptionif multipleOptions & .SecondOption {&nbsp; &nbsp; println("multipleOptions has SecondOption")}let allOptions = MyOptions.Allif allOptions & .ThirdOption {&nbsp; &nbsp; println("allOptions has ThirdOption")}