Animate letters in a label or text view [closed] - ios

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I need to perform an effect like this in my app:
How can I do this? I need to animate single letters in the text and not the entire label. I'm using Swift.
EDIT (more details):
I need to animate the letters from right to left using a sort of spring damping (like UIView animation), but I don't know how to achieve this. The most important part of this animation is the first one, where the letters enter from left to right with a variable space between the first ones and the others

Answer 1

A while back I asked a similar question and got this reply from
https://stackoverflow.com/users/4754400/chris-gulley
A very clever piece of code indeed.
class Timer {
typealias TimerFunction = (Int)->Bool
private var handler: TimerFunction
private var i = 0
init(interval: NSTimeInterval, handler: TimerFunction) {
self.handler = handler
NSTimer.scheduledTimerWithTimeInterval(interval, target: self, selector: "timerFired:", userInfo: nil, repeats: true)
}
#objc
private func timerFired(timer:NSTimer) {
if !handler(i++) {
timer.invalidate()
}
}
}
class ViewController: UIViewController {
let text: NSAttributedString = {
let font = UIFont(name: "Georgia", size: 18.0) ?? UIFont.systemFontOfSize(18.0)
return NSAttributedString(string: "A long time ago, in a galaxy far, far away ...", attributes: [NSFontAttributeName: font])
}()
override func viewDidLoad() {
super.viewDidLoad()
let textView = UITextView(frame: CGRect(x: 100, y: 120, width: CGRectGetWidth(self.view.frame), height: CGRectGetWidth(self.view.frame)-20))
self.view.addSubview(textView)
let _ = Timer(interval: 0.1) {i -> Bool in
textView.attributedText = self.text.attributedSubstringFromRange(NSRange(location: 0, length: i+1))
return i + 1 < self.text.string.characters.count
}
}
}
Displaying text one character at a time in swift 2.0