How to set scheduledTimer in swift and swiftUI?

Swift’s Timer class is a flexible way to schedule work to happen in the future, either just once or repeatedly. In this guide I will to provide a selection of ways to work with it, along with solutions for common problems.

import Foundation

class TimerExample {
    // Timer instance
    private var timer: Timer?
    
    // Start the timer
    func startTimer() {
        // Invalidate any existing timer first
        stopTimer()
        
        // Create a new timer that fires every 120 seconds
        timer = Timer.scheduledTimer(
            timeInterval: 120.0,
            target: self,
            selector: #selector(timerFired),
            userInfo: nil,
            repeats: true
        )
        
        // If you want the timer to continue running while scrolling in a UI
        RunLoop.current.add(timer!, forMode: .common)
        
        print("Timer started - will fire every 120 seconds")
    }
    
    // Stop the timer
    func stopTimer() {
        timer?.invalidate()
        timer = nil
        print("Timer stopped")
    }
    
    // The method that will be called when the timer fires
    @objc private func timerFired() {
        print("Timer fired at: \(Date())")
        
        // Your code to execute every 120 seconds goes here
        performTask()
    }
    
    // Example task to perform when timer fires
    private func performTask() {
        print("Performing scheduled task")
    }
}

// Usage example
let timerExample = TimerExample()
timerExample.startTimer()

// To stop the timer later
// timerExample.stopTimer()

// Keep the program running to see the timer in action
RunLoop.main.run(until: Date(timeIntervalSinceNow: 300))

This code:

1. Creates a TimerExample class that encapsulates timer functionality
2. Sets up a timer to fire every 120 seconds (2 minutes)
3. Includes methods to start and stop the timer
4. Provides a callback method (timerFired) that executes when the timer fires
5. Runs the timer for 300 seconds as an example

If you’re working in a SwiftUI context, you might prefer using this alternative approach:

import SwiftUI

struct ContentView: View {
    @State private var timerCount = 0
    @State private var timer: Timer? = nil
    
    var body: some View {
        VStack {
            Text("Timer count: \(timerCount)")
                .font(.largeTitle)
            
            Button("Start Timer") {
                startTimer()
            }
            .padding()
            
            Button("Stop Timer") {
                stopTimer()
            }
            .padding()
        }
        .onDisappear {
            stopTimer()
        }
    }
    
    func startTimer() {
        stopTimer() // Clear any existing timer
        
        timer = Timer.scheduledTimer(withTimeInterval: 120, repeats: true) { _ in
            timerCount += 1
            print("Timer fired at: \(Date())")
            // Perform your task here
        }
    }
    
    func stopTimer() {
        timer?.invalidate()
        timer = nil
    }
}

Thanks for reading!