什么是Swift？

我试图找到

UIPangestureRecognitor的
方向

我得到了它的一个扩展，其中一个
struct
使用
OptionSet
如下：

extension UIPanGestureRecognizer {
    public struct PanGestureDirection: OptionSet {
        public let rawValue: UInt8

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

        static let Up = PanGestureDirection(rawValue: 1 << 0)
        static let Down = PanGestureDirection(rawValue: 1 << 1)
        static let Left = PanGestureDirection(rawValue: 1 << 2)
        static let Right = PanGestureDirection(rawValue: 1 << 3)
    }

    private func getDirectionBy(velocity: CGFloat, greater: PanGestureDirection, lower: PanGestureDirection) -> PanGestureDirection {
        if velocity == 0 {
            return []
        }
        return velocity > 0 ? greater : lower
    }

    public func direction(in view: UIView) -> PanGestureDirection {
        let velocity = self.velocity(in: view)
        let yDirection = getDirectionBy(velocity: velocity.y, greater: PanGestureDirection.Down, lower: PanGestureDirection.Up)
        let xDirection = getDirectionBy(velocity: velocity.x, greater: PanGestureDirection.Right, lower: PanGestureDirection.Left)
        return xDirection.union(yDirection)
    }
}

扩展UIPAngestureRecognitor{
公共结构泛测试方向：OptionSet{
公众出租价值：UInt8
公共初始化（原始值：UInt8）{
self.rawValue=rawValue
}
静态松弛=测量方向（原始值：1直接从源：

“向位集提供数学集接口的类型。”

FYI-
OptionSet
不是关键字，而是协议的名称。