Swift中的CGPathApply等价或替代？

在Swift 3.0中,您可以使用CGPath.apply,如下所示：

let path: CGPath = ...
// or let path: CGMutablePath

path.apply(info: nil) { (_,elementPointer) in
    let element = elementPointer.pointee
    let command: String
    let pointCount: Int
    switch element.type {
    case .moveToPoint: command = "moveTo"; pointCount = 1
    case .addLineToPoint: command = "lineTo"; pointCount = 1
    case .addQuadCurveToPoint: command = "quadCurveTo"; pointCount = 2
    case .addCurveToPoint: command = "curveTo"; pointCount = 3
    case .closeSubpath: command = "close"; pointCount = 0
    }
    let points = Array(UnsafeBufferPointer(start: element.points,count: pointCount))
    Swift.print("(command) (points)")
}

Swift 2.2

通过添加@convention(c),您现在可以直接从Swift调用CGPathApply.这是一个需要魔法的包装：

extension CGPath {
    func forEach(@noescape body: @convention(block) (CGPathElement) -> Void) {
        typealias Body = @convention(block) (CGPathElement) -> Void
        func callback(info: UnsafeMutablePointer<Void>,element: UnsafePointer<CGPathElement>) {
            let body = unsafeBitCast(info,Body.self)
            body(element.memory)
        }
        print(sizeofValue(body))
        let unsafeBody = unsafeBitCast(body,UnsafeMutablePointer<Void>.self)
        CGPathApply(self,unsafeBody,callback)
    }
}

(请注意,我的代码中没有提及@convention(c),而是在Core Graphics模块的CGPathApply声明中使用.)

使用示例

let path = UIBezierPath(roundedRect: CGRectMake(0,200,100),cornerRadius: 15)
path.CGPath.forEach { element in
    switch (element.type) {
    case CGPathElementType.MoveToPoint:
        print("move((element.points[0]))")
    case .AddLineToPoint:
        print("line((element.points[0]))")
    case .AddQuadCurveToPoint:
        print("quadCurve((element.points[0]),(element.points[1]))")
    case .AddCurveToPoint:
        print("curve((element.points[0]),(element.points[1]),(element.points[2]))")
    case .CloseSubpath:
        print("close()")
    }
}