How to make a button flash or blink?

Question

I am trying to change a button\'s color (just a flash/blink) to green when a scan is correct and red when there\'s a problem. I am able to do this with a view like so

Answer 1

This will start and stop a flashing button onClick, if you only want to flash the button immediately just use the first statement.

var flashing = false

@IBAction func btnFlash_Clicked(sender: AnyObject) {
        if !flashing{
            self.buttonScan.alpha = 1.0
            UIView.animateWithDuration(0.5, delay: 0.0, options: [.CurveEaseInOut, .Repeat, .Autoreverse, .AllowUserInteraction], animations: {() -> Void in
                self.buttonScan.alpha = 0.0
                }, completion: {(finished: Bool) -> Void in
            })

            flashing = true
        }
    else{
        UIView.animateWithDuration(0.1, delay: 0.0, options: [.CurveEaseInOut, .BeginFromCurrentState], animations: {() -> Void in
            self.buttonScan.alpha = 1.0
            }, completion: {(finished: Bool) -> Void in
        })
    }
}

Swift 5.x version

An updated version with extension.

extension UIView {
    func blink(duration: TimeInterval = 0.5, delay: TimeInterval = 0.0, alpha: CGFloat = 0.0) {
        UIView.animate(withDuration: duration, delay: delay, options: [.curveEaseInOut, .repeat, .autoreverse], animations: {
            self.alpha = alpha
        })
    }
}

To call the function:

button.blink() // without parameters
button.blink(duration: 1, delay: 0.1, alpha: 0.2) // with parameters