Typewriter effect text animation

Based on this Answer:
Letter by letter animation for UILabel?

I’ve updated it to Swift 4 and solved the CPU animation problem with DispatchWorkItem in order to create a queue.

Swift 4

extension UILabel {
    func setTextWithTypeAnimation(typedText: String, characterDelay: TimeInterval = 5.0) {
        text = ""
        var writingTask: DispatchWorkItem?
        writingTask = DispatchWorkItem { [weak weakSelf = self] in
            for character in typedText {
                DispatchQueue.main.async {
                    weakSelf?.text!.append(character)
                }
                Thread.sleep(forTimeInterval: characterDelay/100)
            }
        }
        
        if let task = writingTask {
            let queue = DispatchQueue(label: "typespeed", qos: DispatchQoS.userInteractive)
            queue.asyncAfter(deadline: .now() + 0.05, execute: task)
        }
    }
    
}

Usage

label.setTextWithTypeAnimation(typedText: text, characterDelay:  10) //less delay is faster

---

Swift 5

func setTyping(text: String, characterDelay: TimeInterval = 5.0) {
  self.text = ""
    
  let writingTask = DispatchWorkItem { [weak self] in
    text.forEach { char in
      DispatchQueue.main.async {
        self?.text?.append(char)
      }
      Thread.sleep(forTimeInterval: characterDelay/100)
    }
  }
    
  let queue: DispatchQueue = .init(label: "typespeed", qos: .userInteractive)
  queue.asyncAfter(deadline: .now() + 0.05, execute: writingTask)
}

Usage

label.setTyping(text: "Your text")