如何将 DispatchTimeInterval 转换为 NSTimeInterval （或 Double）？

我需要减去一个DispatchTimeInterval从一个NSTimeInterval (or Double).

有没有标准的方法来转换DispatchTimeInterval to an NSTimeInterval?

DispatchTimeInterval是一个枚举：

public enum DispatchTimeInterval : Equatable {
    case seconds(Int)
    case milliseconds(Int)
    case microseconds(Int)
    case nanoseconds(Int)
    case never
}

你可以初始化DispatchTimeInterval using:

    let tenSeconds: DispatchTimeInterval = .seconds(10)
    let tenNanoseconds: DispatchTimeInterval = .nanoseconds(10)

要从枚举中获取值，您需要将值与枚举中的案例值进行匹配

    if case .seconds(let value) = tenSeconds {
        print("DispatchTimeInterval is seconds \(value)")
    } else if case .nanoseconds(let value) = tenNanoseconds {
        print("DispatchTimeInterval is seconds \(value)")
    }

转换函数可能如下所示：

func toDouble(_ interval: DispatchTimeInterval) -> Double? {
        var result: Double? = 0

        switch interval {
        case .seconds(let value):
            result = Double(value)
        case .milliseconds(let value):
            result = Double(value)*0.001
        case .microseconds(let value):
            result = Double(value)*0.000001
        case .nanoseconds(let value):
            result = Double(value)*0.000000001

        case .never:
            result = nil
        }

        return result
    }

有关枚举的更多信息，请参阅 Apple 文档

UPDATE:

创建扩展至DispatchTimeInterval

extension DispatchTimeInterval {
    func toDouble() -> Double? {
        var result: Double? = 0

        switch self {
        case .seconds(let value):
            result = Double(value)
        case .milliseconds(let value):
            result = Double(value)*0.001
        case .microseconds(let value):
            result = Double(value)*0.000001
        case .nanoseconds(let value):
            result = Double(value)*0.000000001

        case .never:
            result = nil
        }

        return result
    }
}