Is there a way to programmatically associate a variable and a target object with the control in swift?

Question

I'm creating a slider programmatically due to and Xcode bug, (don't let me center the thumb when I change the slider values, so I decided to do it using code) and I want to have a variable which saves the slider value. Is there a way to associate the variable and the target object with the control, similar to "addTarget", but instead of an action, its a variable? I don't know if I explained myself but tell me if I need to be more specific. Thanks in advance :) for helping me.

This is my code:

import UIKit 
class ViewController: UIViewController {
    var slider: UISlider!
    @IBOutlet weak var sliderVar: UISlider!
    var currentSliderValue = 0

    override func viewDidLoad() {
      super.viewDidLoad()
      slider = UISlider(frame: CGRect(x: 98, y: 173, width: 699, height: 30))
      slider.center = self.view.center
      slider.minimumValue = 1
      slider.maximumValue = 100
      slider.value = 50
      slider.isContinuous = true
      slider.addTarget(self, action: #selector(sliderMoved(_:)), for: UIControl.Event.valueChanged)
      self.view.addSubview(slider)
    }

    @IBAction func sliderMoved(_ sender: UISlider) {
      currentSliderValue = lroundf(sender.value)
    }
}

My function “sliderMoved” changes the sliderCurrentValue variable, but this var won’t change until I use the slider and move it. I also have a button there, that when you touch it up it shows the slider value, but the “sliderCurrentValue” only changes its value when the slider is moved. I was thinking of creating an IBOutlet but I don’t know how to connect this one with the slider.

Answer 1

As far as I understand you need to bind variable to slider's value. There are several ways to achieve it. There is one way. Declare variable with custom setters and getters

class ViewController: UIViewController {
  var slider: UISlider!

  var sliderValue: Float {
    set {
      // use optional chaining here helps avoid crashes 
      slider?.setValue(newValue, animated: true)
    }
    get {
      // if slider control hasn't created yet you need to return some dummy value
      slider?.value ?? -1
    }
  }

  func viewDidLoad() {
    // your current implementation here
  }
}