How can set a CAShapeLayer transparent in Objective-C?

Question

I'm trying to setup a inset shadow on a UIButton, Thanks to other SO posts, I've managed to do this :

        UIBezierPath *buttonPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds cornerRadius:self.layer.cornerRadius];

        CAShapeLayer* shadowLayer = [CAShapeLayer layer];
        //shadowLayer.cornerRadius = 8.0f;
        [shadowLayer setOpacity:1];
        //[shadowLayer setBackgroundColor:UIColor.redColor.CGColor]; //not working

        // Standard shadow stuff
        [shadowLayer setShadowOpacity:1.0f];
        [shadowLayer setShadowColor:[[UIColor colorWithWhite:1 alpha:1] CGColor]];
        [shadowLayer setShadowOffset:CGSizeMake(2.0f, 2.0f)];
        [shadowLayer setShadowRadius:5];
        // Causes the inner region in this example to NOT be filled.
        [shadowLayer setFillRule:kCAFillRuleEvenOdd];

        // Create the larger rectangle path.
        CGMutablePathRef path = CGPathCreateMutable();
        CGPathAddRect(path, NULL, CGRectInset(self.bounds, -42.0f, -42.0f));
        // Add the inner path so it's subtracted from the outer path.
        CGPathAddPath(path, NULL, buttonPath.CGPath);
        CGPathCloseSubpath(path);

        [shadowLayer setPath:path];
        CGPathRelease(path);

        [self.layer addSublayer:shadowLayer];

I do get a nice white inner shadow, however the shadowLayer adds a black opaque rect (the shadow path).

Tried [shadowLayer setFillColor:UIColor.clearColor.CGColor]; but it removes the shadow as well. Also [shadowLayer setBackgroundColor:UIColor.redColor.CGColor]; does nothing.

How can I get rid of it?!

Answer 1

Adding a [self.layer setMasksToBounds:YES]; solved the issue!