Update for 2018, Swift 4.1:
extension UILabel {
func animate(newText: String, characterDelay: TimeInterval) {
DispatchQueue.main.async {
self.text = ""
for (index, character) in newText.enumerated() {
DispatchQueue.main.asyncAfter(deadline: .now() + characterDelay * Double(index)) {
self.text?.append(character)
}
}
}
}
}
calling it is simple and thread safe:
myLabel.animate(newText: myLabel.text ?? "May the source be with you", characterDelay: 0.3)
@objC, 2012:
Try this prototype function:
- (void)animateLabelShowText:(NSString*)newText characterDelay:(NSTimeInterval)delay
{
[self.myLabel setText:@""];
for (int i=0; i<newText.length; i++)
{
dispatch_async(dispatch_get_main_queue(),
^{
[self.myLabel setText:[NSString stringWithFormat:@"%@%C", self.myLabel.text, [newText characterAtIndex:i]]];
});
[NSThread sleepForTimeInterval:delay];
}
}
and call it in this fashion:
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0),
^{
[self animateLabelShowText:@"Hello Vignesh Kumar!" characterDelay:0.5];
});
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