Question

我正试图在directions中找到UIPanGestureRecognizer
我得到了它的一个扩展，其中一个struct正像这样使用OptionSet：

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)
    }
}

任何人都可以通过简单的例子来简单地帮助我，例如OptionSet的确切含义以及我们如何在将来的任务中使用它？

Answer 1

直接从源头开始

“一种将数学集合接口呈现给位集合的类型。”

https://developer.apple.com/documentation/swift/optionset

Swift中的OptionSet是什么？

1 个答案: