Warning: UICollectionViewFlowLayout has cached frame mismatch for index path 'abc'

Question

This is the code causing the warning:

private override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
    let attributes = super.layoutAttributesForItemAtIndexPath(indexPath)
    let distance = CGRectGetMidX(attributes!.frame) - self.midX;
    var transform = CATransform3DIdentity;
    transform = CATransform3DTranslate(transform, -distance, 0, -self.width);
    attributes!.transform3D = CATransform3DIdentity;
    return attributes
}

The console also prints:

This is likely occurring because the flow layout "xyz" is modifying attributes returned by UICollectionViewFlowLayout without copying them.

How do I fix this warning?

Answer 1

This is likely occurring because the flow layout "xyz" is modifying attributes returned by UICollectionViewFlowLayout without copying them

And sure enough, that's just what you are doing:

private override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
    let attributes = super.layoutAttributesForItemAtIndexPath(indexPath)
    let distance = CGRectGetMidX(attributes!.frame) - self.midX;
    var transform = CATransform3DIdentity;
    transform = CATransform3DTranslate(transform, -distance, 0, -self.width);
    attributes!.transform3D = CATransform3DIdentity;
    return attributes
}

I expect that if you simply say:

let attributes = 
    super.layoutAttributesForItemAtIndexPath(indexPath).copy() 
    as! UICollectionViewLayoutAttributes

or similar, the problem will go away.