Display UIView with a UILabel text mask

Question

I'm trying to add a UIView to a UILabel, so that the text is the view's mask, enabling me to do things like animated text backgrounds (much like the slide to unlock label on the lockscreen).

The way I was planning on doing it was using the mask property on the view's layer to mask it to the shape of the text. However, I cannot find a way to get the UILabel's text shape as a CALayer.

Is this even possible? I can only find solutions that override the -(void)drawRect: method in the UILabel, but this wouldn't give me much flexibility.

Answer 1

UIView added the maskView property in iOS 8.0. Now, just create a UILabel to use as a mask for a UIView:

Objective-C:

UILabel *label = [[UILabel alloc] initWithFrame:self.view.frame];
label.text = @"Label Text";
label.font = [UIFont systemFontOfSize:70];
label.textAlignment = NSTextAlignmentCenter;
label.textColor = [UIColor whiteColor];

UIView* overlayView = [[UIView alloc] initWithFrame:self.view.frame];
overlayView.backgroundColor = [UIColor blueColor];
overlayView.maskView = label;
[self.view addSubview:overlayView];

Swift 2:

let label = UILabel.init(frame: view.frame)
label.text = "Label Text"
label.font = UIFont.systemFontOfSize(70)
label.textAlignment = .Center
label.textColor = UIColor.whiteColor()

let overlayView = UIView.init(frame: view.frame)
overlayView.backgroundColor = UIColor.blueColor()
overlayView.maskView = label
    
view.addSubview(overlayView)

This creates a crisp UILabel with UIColor.blueColor() color taken from overlayView.