Using Auto Layout Constraints for Drag, Pinch, Zoom and Tap

DragZoomPinch.swift

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {
    var redView:UIView!
    var movedRight:Bool = false
    var verticalConstraint:NSLayoutConstraint!
    var horizontalConstraint:NSLayoutConstraint!
    var widthConstraint:NSLayoutConstraint!
    var heightConstraint:NSLayoutConstraint!
    
    var offSet:CGPoint!
    var transform: CGAffineTransform!
    var viewSize:CGSize!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        redView = UIView(frame: CGRect(x: 100, y: 100, width: 200, height: 200))
        redView.backgroundColor = .red
        
        view.addSubview(redView)
        let taps = UITapGestureRecognizer(target: self, action: #selector(tap))
        redView.addGestureRecognizer(taps)
        let drags = UIPanGestureRecognizer(target: self, action: #selector(drag))
        redView.addGestureRecognizer(drags)
        let pinches = UIPinchGestureRecognizer(target: self, action: #selector(pinch))
        redView.addGestureRecognizer(pinches)
        let rotates = UIRotationGestureRecognizer(target: self, action: #selector(rotate))
        redView.addGestureRecognizer(rotates)
        redView.isUserInteractionEnabled = true
        alignView(viewToConstrain: redView)
        
        
    }
    
    @objc func rotate(gest:UIRotationGestureRecognizer) {
        //        view.layoutIfNeeded()
        
        let rotation = gest.rotation
        if let viewToTransform = gest.view {
            switch (gest.state) {
            case .began:
                transform = viewToTransform.transform
                break;
                
            case .changed:
                viewToTransform.transform = transform.concatenating(CGAffineTransform(rotationAngle: rotation))
                break;
                
                
            case .ended:
                break;
                
            default:
                break;
            }
            
        }
        
    }
    
    // see http://stackoverflow.com/a/21803627/1694526
    @objc func drag(gest:UIPanGestureRecognizer) {
        view.layoutIfNeeded()
        
        let translation = gest.translation(in: self.view)
        switch (gest.state) {
        case .began:
            offSet = CGPoint(x: horizontalConstraint.constant, y: verticalConstraint.constant)
            break;
            
        case .changed:
            horizontalConstraint.constant = offSet.x + translation.x
            verticalConstraint.constant = offSet.y + translation.y
            
            view.layoutIfNeeded()
            break;
            
            
        case .ended:
            break;
            
        default:
            break;
        }
        
    }
    @objc func pinch(gest:UIPinchGestureRecognizer) {
        view.layoutIfNeeded()
        let scale = gest.scale
        switch (gest.state) {
        case .began:
            viewSize = CGSize(width: widthConstraint.constant, height: heightConstraint.constant)
            break;
            
        case .changed:
            widthConstraint.constant = viewSize.width * scale
            heightConstraint.constant = viewSize.height * scale
            view.layoutIfNeeded()
            break;
            
        case .ended:
            break;
            
        default:
            break;
        }
        
    }
    
    @objc func tap(gest:UITapGestureRecognizer) {
        if movedRight {
            self.view.layoutIfNeeded()
            self.verticalConstraint.constant += 25
            UIView.animate(withDuration: 0.5){
                self.view.layoutIfNeeded()
                
            }
            
            movedRight = false
            
        }
        else {
            self.view.layoutIfNeeded()
            UIView.animate(withDuration: 0.5){
                self.horizontalConstraint.constant += 25
                self.view.layoutIfNeeded()
                
            }
            movedRight = true
            
        }
    }
    
    func alignView(viewToConstrain:UIView) {
        // a precaution
        viewToConstrain.removeConstraints(viewToConstrain.constraints)
        // enable AutoLayout
        viewToConstrain.translatesAutoresizingMaskIntoConstraints = false
        // set horizontal and vertical constraints
        horizontalConstraint =  viewToConstrain.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        horizontalConstraint.isActive = true
        verticalConstraint = viewToConstrain.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        verticalConstraint.isActive = true
        // set height and width anchors
        heightConstraint =  viewToConstrain.heightAnchor.constraint(equalToConstant: viewToConstrain.frame.height)
        heightConstraint.isActive = true
        widthConstraint = viewToConstrain.widthAnchor.constraint(equalToConstant: viewToConstrain.frame.width)
        widthConstraint.isActive = true
    }
}
let aVC = ViewController()

PlaygroundPage.current.liveView = aVC