您如何枚举Swift中的OptionSetType？

发布时间：2020-12-14 05:50:51 所属栏目：百科来源：网络整理

导读：我在Swift中有一个自定义的OptionSetType结构。如何枚举实例的所有值？这是我的OptionSetType： struct WeekdaySet: OptionSetType { let rawValue: UInt8 init(rawValue: UInt8) { self.rawValue = rawValue } static let Sunday = WeekdaySet(rawValue: 1

我在Swift中有一个自定义的OptionSetType结构。如何枚举实例的所有值？

这是我的OptionSetType：

struct WeekdaySet: OptionSetType {
    let rawValue: UInt8

    init(rawValue: UInt8) {
        self.rawValue = rawValue
    }

    static let Sunday        = WeekdaySet(rawValue: 1 << 0)
    static let Monday        = WeekdaySet(rawValue: 1 << 1)
    static let Tuesday       = WeekdaySet(rawValue: 1 << 2)
    static let Wednesday     = WeekdaySet(rawValue: 1 << 3)
    static let Thursday      = WeekdaySet(rawValue: 1 << 4)
    static let Friday        = WeekdaySet(rawValue: 1 << 5)
    static let Saturday      = WeekdaySet(rawValue: 1 << 6)
}

我想要这样的东西：

let weekdays: WeekdaySet = [.Monday,.Tuesday]
for weekday in weekdays {
    // Do something with weekday
}

在Swift 3中，标准库中没有方法
枚举一个OptionSetType(Swift 2)的元素。
OptionSet(Swift 3)。

这是一个简单地检查每一位的可能的实现
的基本原始值，并且对于设置的每个位，
返回相应的元素。
“溢出乘法”& * 2用作左移，因为<仅针对具体的整数类型定义，但不适用于IntegerType协议。 Swift 2.2：

public extension OptionSetType where RawValue : IntegerType {

    func elements() -> AnySequence<Self> {
        var remainingBits = self.rawValue
        var bitMask: RawValue = 1
        return AnySequence {
            return AnyGenerator {
                while remainingBits != 0 {
                    defer { bitMask = bitMask &* 2 }
                    if remainingBits & bitMask != 0 {
                        remainingBits = remainingBits & ~bitMask
                        return Self(rawValue: bitMask)
                    }
                }
                return nil
            }
        }
    }
}

使用示例

let weekdays: WeekdaySet = [.Monday,.Tuesday]
for weekday in weekdays.elements() {
    print(weekday)
}

// Output:
// WeekdaySet(rawValue: 2)
// WeekdaySet(rawValue: 4)

Swift 3：

public extension OptionSet where RawValue : Integer {

    func elements() -> AnySequence<Self> {
        var remainingBits = rawValue
        var bitMask: RawValue = 1
        return AnySequence {
            return AnyIterator {
                while remainingBits != 0 {
                    defer { bitMask = bitMask &* 2 }
                    if remainingBits & bitMask != 0 {
                        remainingBits = remainingBits & ~bitMask
                        return Self(rawValue: bitMask)
                    }
                }
                return nil
            }
        }
    }
}

（编辑：李大同）

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