strokePath.swift

//: A UIKit based Playground for presenting user interface
  
import UIKit
import PlaygroundSupport

class HexagonView: UIView {
    
    private let borderLineWidth: CGFloat = 4
    var borderLineColor: UIColor = .clear
    
    override func draw(_ rect: CGRect) {
        let maskLayer = CAShapeLayer()
        maskLayer.fillRule = kCAFillRuleEvenOdd
        maskLayer.frame = bounds
        
        let path = maskPath
        
        guard let context = UIGraphicsGetCurrentContext() else { return }
        context.setStrokeColor(borderLineColor.cgColor)
        context.setLineWidth(borderLineWidth)
        context.addPath(path.cgPath)
        context.strokePath()
        
        maskLayer.path = path.cgPath
        
        layer.mask = maskLayer
    }
    
    var maskPath: UIBezierPath {
        let width = frame.size.width
        let height = frame.size.height
        let hPadding = width * 1 / 8 / 2
        
        let path = UIBezierPath()
        path.move(to: CGPoint(x: width / 2, y: 0))
        path.addLine(to: CGPoint(x: width - hPadding, y: height / 4))
        path.addLine(to: CGPoint(x: width - hPadding, y: height * 3 / 4))
        path.addLine(to: CGPoint(x: width / 2, y: height))
        path.addLine(to: CGPoint(x: hPadding, y: height * 3 / 4))
        path.addLine(to: CGPoint(x: hPadding, y: height / 4))
        path.close()
        
        return path
    }
    
}

class MyViewController : UIViewController {
    override func loadView() {
        let view = UIView()
        view.backgroundColor = .white

        let hexagon = HexagonView()
        hexagon.frame = CGRect(x: 150, y: 200, width: 200, height: 200)
        hexagon.borderLineColor = UIColor.red
        
        view.addSubview(hexagon)
        self.view = view
    }
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()