Slide to unlock Animation

   // Slide to unlock Animation
    CALayer *maskLayer = [CALayer layer];
    maskLayer.backgroundColor = [[UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.55f] CGColor];
    maskLayer.contents = (id)[[UIImage imageNamed:@"mask.png"] CGImage];
    maskLayer.contentsGravity = kCAGravityCenter;
    maskLayer.frame = CGRectMake(self.frame.size.width * -1, 0.0f, self.frame.size.width * 2, self.frame.size.height);
    CABasicAnimation *maskAnim = [CABasicAnimation animationWithKeyPath:@"position.x"];
    maskAnim.byValue = [NSNumber numberWithFloat:self.frame.size.width];
    maskAnim.repeatCount = HUGE_VAL;
    maskAnim.duration = 2.0f;
    [maskLayer addAnimation:maskAnim forKey:@"slideAnim"];
    self.layer.mask = maskLayer;