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Converting Between View Coordinate Systems
import UIKit
import PlaygroundSupport
class MyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Main view
view.backgroundColor = .black
view.frame = CGRect(x: 0, y: 0, width: 500, height: 500)
// Red view
let redView = UIView(frame: CGRect(x: 20, y: 20, width: 460, height: 460))
redView.backgroundColor = .red
view.addSubview(redView)
// Blue view
let blueView = UIView(frame: CGRect(x: 20, y: 20, width: 420, height: 420))
blueView.backgroundColor = .blue
redView.addSubview(blueView)
// Orange view
let orangeView = UIView(frame: CGRect(x: 20, y: 20, width: 380, height: 380))
orangeView.backgroundColor = .orange
blueView.addSubview(orangeView)
// Yellow view
let yellowView = UIView(frame: CGRect(x: 20, y: 20, width: 340, height: 100))
yellowView.backgroundColor = .yellow
orangeView.addSubview(yellowView)
// Let's try to convert now
var resultFrame = CGRect.zero
let randomRect: CGRect = CGRect(x: 0, y: 0, width: 100, height: 50)
/*
func convert(CGRect, from: UIView?)
Converts a rectangle from the coordinate system of another view to that of the receiver.
*/
// The following line converts a rectangle (randomRect) from the coordinate system of yellowView to that of self.view:
resultFrame = view.convert(randomRect, from: yellowView)
// Try also one of the following to get a feeling of how it works:
// resultFrame = view.convert(randomRect, from: orangeView)
// resultFrame = view.convert(randomRect, from: redView)
// resultFrame = view.convert(randomRect, from: nil)
/*
func convert(CGRect, to: UIView?)
Converts a rectangle from the receiver’s coordinate system to that of another view.
*/
// The following line converts a rectangle (randomRect) from the coordinate system of yellowView to that of self.view
resultFrame = yellowView.convert(randomRect, to: view)
// Same as what we did above, using "from:"
// resultFrame = view.convert(randomRect, from: yellowView)
// Also try:
// resultFrame = orangeView.convert(randomRect, to: view)
// resultFrame = redView.convert(randomRect, to: view)
// resultFrame = orangeView.convert(randomRect, to: nil)
// Add an overlay with the calculated frame to self.view
let overlay = UIView(frame: resultFrame)
overlay.backgroundColor = UIColor(white: 1.0, alpha: 0.9)
overlay.layer.borderColor = UIColor.black.cgColor
overlay.layer.borderWidth = 1.0
view.addSubview(overlay)
}
}
var ctrl = MyViewController()
PlaygroundPage.current.liveView = ctrl.view
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