Draw dynamic line path - sample

DrawLines.swift

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

class CustomButton: UIButton {
	var key: String?
	
	convenience init(key: String, point: CGPoint) {
		self.init(type: .custom)
		self.key = key
		self.frame.size = CGSize(width: 16, height: 16)
		self.center = point
		self.backgroundColor = .black
		self.layer.masksToBounds = true
		self.layer.cornerRadius = 8.0
	}
}

class MyViewController : UIViewController {
	
	let points = [
		("A", CGPoint(x: 20, y: 400)),
		("B", CGPoint(x: 50, y: 350)),
		("C", CGPoint(x: 80, y: 350)),
		("D", CGPoint(x: 110, y: 300)),
		("E", CGPoint(x: 200, y: 400)),
		("F", CGPoint(x: 230, y: 375)),
		]
	
	var startKey: String?
	var endKey: String?
	
	var activeLineImageView: UIImageView?
	
    override func loadView() {
        let view = UIView()
        view.backgroundColor = .white
		view.frame.size = CGSize(width: 500, height: 500)
		self.view = view
		
		
		
		UIGraphicsBeginImageContextWithOptions(view.frame.size, false, 0)
		let path = UIBezierPath()
		path.lineWidth = 5.0
		path.move(to: points[0].1)
		
		points.forEach { point in
			let button = CustomButton(key: point.0, point: point.1)
			button.addTarget(self, action: #selector(buttonPressed), for: .touchUpInside)
			view.addSubview(button)
			
			path.addLine(to: point.1)
		}
		
		UIColor.black.setStroke()
		path.stroke()
		
		var image = UIGraphicsGetImageFromCurrentImageContext()
		var imageView = UIImageView(image: image)
		self.view.addSubview(imageView)
		UIGraphicsEndImageContext()
    }
	
	@objc private func buttonPressed(_ button: CustomButton) {
		if startKey == nil && endKey == nil {
			activeLineImageView?.removeFromSuperview()
			activeLineImageView = nil
			startKey = button.key
			return
		}
		
		if startKey != nil && endKey == nil {
			endKey = button.key
		
			drawLine()
			resetKeys()
		}
	}
	
	private func drawLine() {
		
		UIGraphicsBeginImageContextWithOptions(view.frame.size, false, 0)
		let path = UIBezierPath()
		path.lineWidth = 3.0
		
		var add = false
		
		for point in points {
			
			if let startKey = startKey, startKey == point.0 {
				path.move(to: point.1)
				add = true
				continue
			}
			
			if let endKey = endKey, endKey == point.0 {
				path.addLine(to: point.1)
				add = false
				break
			}
			
			if add {
				path.addLine(to: point.1)
				continue
			}
		}
		
		UIColor.red.setStroke()
		path.stroke()
		
		var image = UIGraphicsGetImageFromCurrentImageContext()
		activeLineImageView = UIImageView(image: image)
		self.view.addSubview(activeLineImageView!)
		UIGraphicsEndImageContext()
	}
	
	private func resetKeys() {
		startKey = nil
		endKey = nil
	}
}

// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()