SuperView becomes null after adding sublayers but the image is still visible - ios

Question

I am using MKNetwrkKit. I have an imageView, I have added it as a subView to a UIView. I download an image using "UIImageView+MKNetworkKitAdditions.h". I add a mask to the ImageView and remove it from superView, before the download is completed, and I get a crash!
- (void) testUIImageViewDownloadCrash {
UIImageView *imageView = [[UIImageView alloc] init];
[imageView mk_setImageAtURL:[NSURL URLWithString:#"http://www.gravatar.com/avatar/a717291747c76567bb0f086e15ae6e43?s=32&d=identicon&r=PG"] onCompletion:^(BOOL success, BOOL fromCache) {
//
}];
UIView *view = [[UIView alloc] init];
[view addSubview:imageView];
[self addMaskToImageView:imageView];
[imageView removeFromSuperview];
}
Now, the weird thing is, this crash occurs only when I add the mask... here is the function that adds the mask.
- (CAGradientLayer*) addMaskToImageView:(UIImageView *) inImageView
{
CALayer *imageLayer = inImageView.layer;
CGRect imageBounds = imageLayer.bounds;
CGRect ellipseRect = CGRectInset(imageBounds, 4, 4);
CGPathRef maskPath = CGPathCreateWithEllipseInRect(ellipseRect, NULL);
if (maskPath)
{
CAShapeLayer *maskLayer = [CAShapeLayer layer];
maskLayer.bounds = imageBounds;
maskLayer.position = (CGPoint){CGRectGetMidX(imageBounds), CGRectGetMidY(imageBounds)};
maskLayer.path = maskPath;
maskLayer.fillColor = [UIColor blackColor].CGColor;
imageLayer.mask = maskLayer;
CFRelease(maskPath);
}
CAGradientLayer *gradientRingLayer = [self createGradientRing:imageBounds];
CALayer *containerLayer = [CALayer layer];
[imageLayer.superlayer addSublayer:containerLayer];
// Move container layer to the image position
containerLayer.position = imageLayer.position;
// Image is now at 0,0 in the container
imageLayer.position = CGPointZero;
[containerLayer addSublayer:gradientRingLayer];
[containerLayer addSublayer:imageLayer];
layer.shouldRasterize = YES;
layer.rasterizationScale = [[UIScreen mainScreen] scale];
layer.contentsScale = [[UIScreen mainScreen] scale];
containerLayer.shadowColor = [UIColor blackColor].CGColor;
containerLayer.shadowOpacity = 1.0f;
containerLayer.shadowOffset = CGSizeMake(2.0f, 5.0f);
containerLayer.shadowRadius = 7.5f;
// Create shadow at the righ place around the image
CGPathRef containerShadowPath = CGPathCreateWithEllipseInRect(imageLayer.frame, NULL);
containerLayer.shadowPath = containerShadowPath;
CFRelease(containerShadowPath);
return gradientRingLayer;
}
- (CAGradientLayer*)createGradientRing:(CGRect)inBounds {
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.anchorPoint = CGPointMake(0.5f, 0.5f);
gradient.position = CGPointMake(0.0f, 0.0f);
// gradient.startPoint = CGPointMake(0.0,0.0);
// gradient.endPoint = CGPointMake(0.0,0.0);
gradient.bounds = inBounds;
gradient.cornerRadius = 0.0;
gradient.colors = [NSArray arrayWithObjects:
(id)[UIColor ringLight].CGColor,
(id)[UIColor ringLight].CGColor,
nil];
CAShapeLayer *frameLayer = [CAShapeLayer layer];
CGPathRef framePath = CGPathCreateWithEllipseInRect(CGRectInset(inBounds, 0, 0), NULL);
if (framePath)
{
frameLayer.bounds = inBounds;
frameLayer.position = (CGPoint){CGRectGetMidX(inBounds), CGRectGetMidY(inBounds)};
frameLayer.path = framePath;
frameLayer.fillColor = [UIColor blackColor].CGColor;
CFRelease(framePath);
}
gradient.mask = frameLayer;
return gradient;
}
If I comment out adding the mask, it won't crash. Another thing that I don't understand is, after adding the mask, if do this:
NSLog(#"subviews count : %i",[view.subviews count]);
then I get 0! Where did the imageView go?
I observed that the addMask function is making a superView of the imageView null. I found out that the line [containerLayer addSublayer:imageLayer]; is the culprit. This is making the superView of the imageView null. But why? And how can I fix it?
Sometimes I get this exception too, and I don't know why.
-[__NSCFString sublayers]: unrecognized selector sent to instance
I tried on iOS 5 and iOS 6.