How to change button repeatedly when tapped?

Question

Using Swift, how do I make a:

1. Button with words "start", that changes to "pause" and vice versa when tapped? Not just once, but can be done infinitely? (e.g. in a stopwatch app)
2. Custom image button that changes between 2 image when tapped, that can also be done (tapped & change) infinitely?

Answer 1

Step 1: Create a Bool variable

var isPlaying:Bool = false

Step 2: Connect your button with this IBAction method:

@IBAction func btnStartStop(sender: UIButton) {
    if isPlaying{

        isPlaying = false
        sender.setTitle("Pause", forState: UIControlState.Normal)
        sender.setImage(pauseImage, forState: .Normal)
        //Pause Stopwatch
    }
    else{

        isPlaying = true
        sender.setTitle("Play", forState: UIControlState.Normal)
        sender.setImage(playImage, forState: .Normal)
      //Play Stopwatch
    }
  }