Run repeating function in Swift - ios

Question

I want to make a label blink forever. Simplified version of my code:
func blink (label: UILabel) -> Void {
let text = label.text
label.text = ""
sleep(1)
label.text = text
sleep(2)
print("blinking")
blink(label: label)
}
override func viewDidLoad() {
super.viewDidLoad()
label = getLabel()
blink(label: label)
}
The view never loads, because its waiting for the Blink function to finish, which it never does. How can I make this function work, but not wait for it to complete itself (witch it never will) before the rest of my code can run?

Answer 1

This will run a timer, with a 1 second interval, which will repeat. Just invalidate the timer if you don't want to use it anymore. Ideally call it when the controller is deinitialized.
let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { (timer) in
blink(label: label)
}
Also instead of using sleep... try using UIView like this:
UIView.animate(withDuration: 1, animations: {
//do animtions
}) { (completed) in
// repeat or finish
}

Answer 2

It is handy to have a separate class for this action, to ensure you will not have some concurrency and memory allocation problems
So you can create some class like this one
class Blink {
typealias BlinkBlock = (Bool) -> ()
private var timer: Timer?
private let interval: TimeInterval
private let blinkBlock: BlinkBlock
private var blinkState: Bool = true {
didSet {
DispatchQueue.main.async {
self.blinkBlock(self.blinkState)
}
}
}
init(interval: TimeInterval, blinkBlock: #escaping BlinkBlock) {
self.blinkBlock = blinkBlock
self.interval = interval
}
deinit {
timer?.invalidate()
}
func startBlinking() {
stopBlinking()
timer = Timer.scheduledTimer(timeInterval: interval,
target: self,
selector: #selector(onTimer),
userInfo: nil,
repeats: true)
blinkState = true
}
func stopBlinking() {
timer?.invalidate()
timer = nil
}
#objc
func onTimer() {
blinkState = !blinkState
}
}
and then in your view controller just
var blink: Blink?
override func viewDidLoad() {
let text = label.text
blink = blink(interval: 1) {
label.text = $0 ? text : ""
print("blinking")
}
blink?.startBlinking()
}
This will not block main thread and will safely invalidate timer on deallocation

Answer 3

You should create class inherited form UILabel. After that you create function repeat reply on timer. Please follow the code:
class CustomLabel: UILabel {
var timer: Timer?
var counter = 0
deinit {
timer?.invalidate()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.fireTimer()
}
override init(frame: CGRect) {
super.init(frame: frame)
self.fireTimer()
}
func fireTimer(){
timer = Timer.scheduledTimer(timeInterval: 1.0,
target: self,
selector: #selector(waittingAnimation),
userInfo: nil,
repeats: true)
}
#objc func waittingAnimation(){
self.isHidden = !(self.isHidden)
}
}
in your viewcontroller you call fireTimer() to execute animation
#IBOutlet weak var customLabel: CustomLabel!
override func viewDidLoad() {
super.viewDidLoad()
self.customLabel.text = "ABC"
self.customLabel.fireTimer()
}