Прозрачный градиент как фон UIView

Создаст градиент слева направо

UIView* view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
view.backgroundColor = [UIColor whiteColor];
 
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = view.bounds;
 
gradientLayer.colors = [NSArray arrayWithObjects:
                            (id)[UIColor clearColor].CGColor,
                            (id)[UIColor whiteColor].CGColor, nil];
 
[gradientLayer setStartPoint:CGPointMake(0.0, 1.0)];
[gradientLayer setEndPoint:CGPointMake(1.0, 1.0)];
 
view.layer.mask= gradientLayer;