A quick guide to the swift timer

Easy examples to basic swift timer functionality like passing user info, creating repeating swift timers invalidating swift timers and more

Creating Non Repeating Swift Timer

A non-repeating timer can be created in two ways. We will create timers with 1-second durations in examples given below

Passing @objc function

let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(tick), userInfo: nil, repeats: false)
// add @objc to function to make it accessible from objective-c code
@objc func tick() {
    print("Hi")
}

Using a block

We can also use a block and execute our code in that

let timer3 = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: false) { (timer) in
            print ("hello")
    }

Creating a Repeating timer

A repeating timer keeps on firing at fixed intervals till it is invalidated. A swift timer can be made to repeat simply by passing true in repeats:

       let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(tick), userInfo: nil, repeats: true) // repeats is true

In the case of blocks, we can create a repeating timer in same fashion

let timer3 = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { (timer) in
           print ("hello")
  }

Passing data through timer

We can use userinfo: to add data to a timer event. This can be any information regarding timer fire. A simple example is

let timer2 = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(tick), userInfo: ["foo":"val"], repeats: false)

In order to extract the userinfo: in tik() we need to accept the timer instance as a parameter and get userinfo from it. An example is given below

@objc func tick(timer:Timer) {
        if let info = timer.userInfo as? [String:String] {
            print(info["foo"])
        }
    }

Invalidating a repeating Swift Timer

A repeating swift timer can be invalidated simply by calling invalidate() on its instance. This can be achieved either by keeping the reference as shown below

  let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(tick), userInfo: nil, repeats: true)
@objc func tick() {
        print("Hi")
    }
timer.invalidate()

Or from within the function by using timer reference

 let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(tick), userInfo: nil, repeats: true)
  @objc func tick(timer:Timer) {
        print("Hi")
      if <your condition> {
          timer.invalidate()
       }
    }

If you are using blocks then also you can use the timer reference to invalidate a swift timer.

let timer3 = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { (timer) in
           print ("hello")
        if <your condition> {
           timer.invalidate()
        }
  }

Hope it helps!!!