How to update Counter's value inside a Label of another class?-CodePudding

I have a counting-upward object in StopWatch class and a label showing its value in ViewController class. I used @Published and @ObservedObject property wrappers for sharing and observing counter's value.

How could I automatically update counter's value in a label?

ViewController.swift

import UIKit
import SwiftUI

class ViewController: UIViewController {
    
    @ObservedObject var stopWatch = StopWatch()
    @IBOutlet var label: UILabel!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        label.text = "\(self.stopWatch.counter)"
    }

    @IBAction func start(_ sender: UIButton) { self.stopWatch.start() }
    @IBAction func stop(_ sender: UIButton) { self.stopWatch.stop() }
}

StopWatch.swift

class StopWatch: ObservableObject {
    
    @Published var counter: Int = 0
    var timer = Timer()
    
    func start() {
        self.timer = Timer.scheduledTimer(withTimeInterval: 1.0, 
                                                   repeats: true) { _ in
            self.counter  = 1
        }
    }
    func stop() {
        self.timer.invalidate()
    }
}

CodePudding user response：

The @ObservedObject works only inside SwiftUI view. In this case it is possible to observe published property directly via Publisher, like

import Combine
class ViewController: UIViewController {

    let stopWatch = StopWatch()
    @IBOutlet var label: UILabel!

    private var cancellable: AnyCancellable!
    override func viewDidLoad() {
        super.viewDidLoad()
        cancellable = stopWatch.$counter.sink { [weak self] newValue in
            self?.label.text = "\(newValue)"
        }
    }

// ... other code