Auto layout constraint and CALayer issue - ios

Question

I am using this code to make my top corners to be rounded.
- (void)setMaskTo:(UIView*)view byRoundingCorners:(UIRectCorner)corners
{
UIBezierPath *rounded = [UIBezierPath bezierPathWithRoundedRect:view.bounds
byRoundingCorners:corners
cornerRadii:CGSizeMake(5.0, 5.0)];
CAShapeLayer *shape = [[CAShapeLayer alloc] init];
[shape setPath:rounded.CGPath];
view.layer.mask = shape;
}
then in initWithFrame of superview method I make this:
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectZero];
[self setMaskTo:imageView byRoundingCorners:UIRectCornerTopLeft|UIRectCornerTopRight];
But as result of it I don't see image. I am using auto layout constraint that works correct and I see image in case if I don't use rounding corner method above. But if I use it, I don't see image.
Seems if use draw rect callback of my view where image is placed, I can set rounding corners. But in this case if view contains other views it will add rounding to all subviews, if I will cycle it:
It works but for all subviews of course:
- (void)drawRect:(CGRect)rect {
// Drawing code
for (UIView *view in self.subviews)
{
[self setMaskTo:view byRoundingCorners:UIRectCornerTopLeft|UIRectCornerTopRight];
}
}
- (void)setMaskTo:(UIView*)view byRoundingCorners:(UIRectCorner)corners
{
UIBezierPath *rounded = [UIBezierPath bezierPathWithRoundedRect:view.bounds
byRoundingCorners:corners
cornerRadii:CGSizeMake(5.0, 5.0)];
CAShapeLayer *shape = [[CAShapeLayer alloc] init];
[shape setPath:rounded.CGPath];
view.layer.mask = shape;
}
So how to detect when image view has got frame, I suppose that the frame is nil at start CALayer does not understand how to interact with view.

Answer 1

That's happen because you instantiate the view with frame CGRectZero, then you use that bounds for the mask so nothing in the view is inside the mask and therefore nothing is shown.
As a work around you can set a tag to UIImageView instance different than 0 and search in the subviews for that
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectZero];
imageView.tag = 111; //or any other number you want
- (void)drawRect:(CGRect)rect {
// Drawing code
for (UIView *view in self.subviews)
{
if (view.tag==111){[self setMaskTo:view byRoundingCorners:UIRectCornerTopLeft|UIRectCornerTopRight];
}}
}
- (void)setMaskTo:(UIView*)view byRoundingCorners:(UIRectCorner)corners
{
UIBezierPath *rounded = [UIBezierPath bezierPathWithRoundedRect:view.bounds
byRoundingCorners:corners
cornerRadii:CGSizeMake(5.0, 5.0)];
CAShapeLayer *shape = [[CAShapeLayer alloc] init];
[shape setPath:rounded.CGPath];
view.layer.mask = shape;
}

Answer 2

If I understand it correctly, you want your UIView, which contains an image inside, to have rounded corners on the top side, right? Then you could just resize the mask layer in layoutSubviews.
Something like:
- (void)awakeFromNib {
[super awakeFromNib];
[self setMaskTo:self byRoundingCorners:UIRectCornerTopLeft|UIRectCornerTopRight];
}
- (void)layoutSubviews {
[super layoutSubviews];
self.layer.mask.frame = self.layer.bounds;
}
- (void)setMaskTo:(UIView*)view byRoundingCorners:(UIRectCorner)corners {
UIBezierPath *rounded = [UIBezierPath bezierPathWithRoundedRect:view.bounds
byRoundingCorners:corners
cornerRadii:CGSizeMake(5.0, 5.0)];
CAShapeLayer *shape = [[CAShapeLayer alloc] init];
[shape setPath:rounded.CGPath];
view.layer.mask = shape;
view.layer.masksToBounds = YES;
}