在苹果关于与C-marked交互的文档中,它们描述了将NS_ENUM
APIs样式枚举导入为Swift枚举的方式。这是有道理的,而且由于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。
再往下看,关于NS_OPTIONS
-marked C风格的选项是这样的:
Swift还导入用
NS_OPTIONS
宏标记的选项。虽然选项的行为类似于导入的枚举,但选项还可以支持一些按位操作,如&
、|
和~
。在Objective-C中,您使用常量零(0
)表示一个空的期权集。在Swift中,使用nil
表示缺少任何选项。
假设Swift中没有options
值类型,我们如何创建一个C风格的options变量来使用呢?
发布于 2014-06-06 01:09:54
Swift 3.0
几乎与Swift 2.0完全相同。OptionSetType被重命名为OptionSet,按照约定,枚举是小写的。
struct MyOptions : OptionSet {
let rawValue: Int
static let firstOption = MyOptions(rawValue: 1 << 0)
static let secondOption = MyOptions(rawValue: 1 << 1)
static let thirdOption = MyOptions(rawValue: 1 << 2)
}
Swift 3的建议是简单地使用空数组文字,而不是提供none
选项:
let noOptions: MyOptions = []
其他用法:
let singleOption = MyOptions.firstOption
let multipleOptions: MyOptions = [.firstOption, .secondOption]
if multipleOptions.contains(.secondOption) {
print("multipleOptions has SecondOption")
}
let allOptions = MyOptions(rawValue: 7)
if allOptions.contains(.thirdOption) {
print("allOptions has ThirdOption")
}
Swift 2.0
在SWIFT2.0中,协议扩展负责处理这些模板的大部分内容,这些模板现在作为符合OptionSetType
的结构导入。(RawOptionSetType
在Swift 2 beta 2中消失了。)声明要简单得多:
struct MyOptions : OptionSetType {
let rawValue: Int
static let None = MyOptions(rawValue: 0)
static let FirstOption = MyOptions(rawValue: 1 << 0)
static let SecondOption = MyOptions(rawValue: 1 << 1)
static let ThirdOption = MyOptions(rawValue: 1 << 2)
}
现在我们可以在MyOptions
中使用基于集合的语义了
let singleOption = MyOptions.FirstOption
let multipleOptions: MyOptions = [.FirstOption, .SecondOption]
if multipleOptions.contains(.SecondOption) {
print("multipleOptions has SecondOption")
}
let allOptions = MyOptions(rawValue: 7)
if allOptions.contains(.ThirdOption) {
print("allOptions has ThirdOption")
}
Swift 1.2
查看Swift导入的Objective-C选项(例如,UIViewAutoresizing
),我们可以看到选项被声明为符合协议RawOptionSetType
的struct
,该协议又符合_RawOptionSetType
、Equatable
、RawRepresentable
、BitwiseOperationsType
和NilLiteralConvertible
。我们可以像这样创建我们自己的:
struct MyOptions : RawOptionSetType {
typealias RawValue = UInt
private var value: UInt = 0
init(_ value: UInt) { self.value = value }
init(rawValue value: UInt) { self.value = value }
init(nilLiteral: ()) { self.value = 0 }
static var allZeros: MyOptions { return self(0) }
static func fromMask(raw: UInt) -> MyOptions { return self(raw) }
var rawValue: UInt { return self.value }
static var None: MyOptions { return self(0) }
static var FirstOption: MyOptions { return self(1 << 0) }
static var SecondOption: MyOptions { return self(1 << 1) }
static var ThirdOption: MyOptions { return self(1 << 2) }
}
现在,我们可以像苹果文档中描述的那样处理这个新的选项集MyOptions
:您可以使用enum
-like语法:
let opt1 = MyOptions.FirstOption
let opt2: MyOptions = .SecondOption
let opt3 = MyOptions(4)
它的行为也像我们所期望的选项的行为:
let singleOption = MyOptions.FirstOption
let multipleOptions: MyOptions = singleOption | .SecondOption
if multipleOptions & .SecondOption != nil { // see note
println("multipleOptions has SecondOption")
}
let allOptions = MyOptions.fromMask(7) // aka .fromMask(0b111)
if allOptions & .ThirdOption != nil {
println("allOptions has ThirdOption")
}
我已经构建了一个没有所有查找/替换的generator to create a Swift option set。
最新版本:针对Swift 1.1测试版3的修改。
发布于 2014-10-01 05:14:05
Xcode6.1Beta2给RawOptionSetType
协议带来了一些变化(参见这个Airspeedvelocity blog entry和Apple release notes)。
基于Nate Cooks的例子,这里是一个更新的解决方案。您可以像这样定义自己的选项集:
struct MyOptions : RawOptionSetType, BooleanType {
private var value: UInt
init(_ rawValue: UInt) { self.value = rawValue }
// MARK: _RawOptionSetType
init(rawValue: UInt) { self.value = rawValue }
// MARK: NilLiteralConvertible
init(nilLiteral: ()) { self.value = 0}
// MARK: RawRepresentable
var rawValue: UInt { return self.value }
// MARK: BooleanType
var boolValue: Bool { return self.value != 0 }
// MARK: BitwiseOperationsType
static var allZeros: MyOptions { return self(0) }
// MARK: User defined bit values
static var None: MyOptions { return self(0) }
static var FirstOption: MyOptions { return self(1 << 0) }
static var SecondOption: MyOptions { return self(1 << 1) }
static var ThirdOption: MyOptions { return self(1 << 2) }
static var All: MyOptions { return self(0b111) }
}
然后可以像这样使用它来定义变量:
let opt1 = MyOptions.FirstOption
let opt2:MyOptions = .SecondOption
let opt3 = MyOptions(4)
像这样测试bits:
let singleOption = MyOptions.FirstOption
let multipleOptions: MyOptions = singleOption | .SecondOption
if multipleOptions & .SecondOption {
println("multipleOptions has SecondOption")
}
let allOptions = MyOptions.All
if allOptions & .ThirdOption {
println("allOptions has ThirdOption")
}
发布于 2015-06-28 19:01:23
文档中的Swift 2.0示例:
struct PackagingOptions : OptionSetType {
let rawValue: Int
init(rawValue: Int) { self.rawValue = rawValue }
static let Box = PackagingOptions(rawValue: 1)
static let Carton = PackagingOptions(rawValue: 2)
static let Bag = PackagingOptions(rawValue: 4)
static let Satchel = PackagingOptions(rawValue: 8)
static let BoxOrBag: PackagingOptions = [Box, Bag]
static let BoxOrCartonOrBag: PackagingOptions = [Box, Carton, Bag]
}
你可以在here上找到它
https://stackoverflow.com/questions/24066170
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