pan gesture recongizer not working with if statement - swift

Question

In my swift code below i have 2 objects with the goal of only one of them having a pan gesture applied to them at a time. Right now my code works with one of the boxes but when the if statement is applied I can control the other box by touching the first box. I can dragged and drop both boxes when the correct if statement is applied.
import UIKit
class ViewController: UIViewController {
var frontBox = UIButton()
var backBox = UIButton()
var selectorB = UIButton()
var selctorValue = 0
var panGesture = UIPanGestureRecognizer()
// constraint we will modify when slider is changed
var backBoxWidth: NSLayoutConstraint!
// constraints we will modify when backBox is dragged
var backBoxCenterY: NSLayoutConstraint!
var backBoxLeading: NSLayoutConstraint!
var FrontBoxWidth: NSLayoutConstraint!
// constraints we will modify when backBox is dragged
var FrontBoxCenterY: NSLayoutConstraint!
var FrontBoxLeading: NSLayoutConstraint!
var tim = 50.0
override func viewDidLoad() {
super.viewDidLoad()
[backBox,selectorB,frontBox].forEach{
$0.translatesAutoresizingMaskIntoConstraints = false
view.addSubview($0)
$0.backgroundColor = UIColor(
red: .random(in: 0.0...1),
green: .random(in: 0.9...1),
blue: .random(in: 0.7...1),
alpha: 1
)
}
NSLayoutConstraint.activate([
selectorB.bottomAnchor.constraint(equalTo: view.bottomAnchor),
selectorB.leadingAnchor.constraint(equalTo: view.leadingAnchor),
selectorB.heightAnchor.constraint(equalTo: view.heightAnchor,multiplier: 0.1),
selectorB.widthAnchor.constraint(equalTo: view.widthAnchor,multiplier: 1),
])
// backBox Width constraint
backBoxWidth = backBox.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.2)
// backBox CenterY constraint
backBoxCenterY = backBox.centerYAnchor.constraint(equalTo: view.centerYAnchor)
// backBox Leading constraint
backBoxLeading = backBox.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: CGFloat(tim))
// backBox Width constraint
FrontBoxWidth = frontBox.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.2)
// backBox CenterY constraint
FrontBoxCenterY = frontBox.centerYAnchor.constraint(equalTo: view.centerYAnchor)
// backBox Leading constraint
FrontBoxLeading = frontBox.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: CGFloat(tim))
NSLayoutConstraint.activate([
// backBox Height is constant
backBox.heightAnchor.constraint(equalTo: view.heightAnchor,multiplier: 0.5),
backBoxWidth,
backBoxLeading,
backBoxCenterY,
frontBox.heightAnchor.constraint(equalTo: view.heightAnchor,multiplier: 0.3),
FrontBoxWidth,
FrontBoxCenterY,
FrontBoxLeading,
])
panGesture = UIPanGestureRecognizer(target: self, action: #selector(draggedView(_:)))
selectorB.addTarget(self, action: #selector(press), for: .touchDown)
frontBox.addGestureRecognizer(panGesture)
backBox.addGestureRecognizer(panGesture)
frontBox.isUserInteractionEnabled = true
backBox.isUserInteractionEnabled = true
}
#objc func draggedView(_ sender: UIPanGestureRecognizer) {
if selctorValue == 1 {
// update backBox Leading and CenterY constraints
let translation = sender.translation(in: self.view)
backBoxLeading.constant += translation.x
backBoxCenterY.constant += translation.y
sender.setTranslation(CGPoint.zero, in: self.view)
}
else {
let translation = sender.translation(in: self.view)
FrontBoxLeading.constant += translation.x
FrontBoxCenterY.constant += translation.y
sender.setTranslation(CGPoint.zero, in: self.view)
}
}
#objc func press(){
selctorValue = selctorValue == 0 ? 1 : 0
}
}
[![enter image description here][1]][1]

Answer 1

Eliminate the if statement and use object oriented programming. One pan gesture recognizer for different views is silly. Gesture recognizers can be enabled or disabled. So just give each view its own pan gesture recognizer and have the button toggle which one is enabled.