UICollectionViewCell上的奇怪边框-Swift

Question

I have created a subclass for a UICollectionViewCell, which looks like this...

import Foundation
import UIKit
class GroupCollectionViewCell: UICollectionViewCell {
    @IBOutlet weak var name: UILabel!
    @IBOutlet weak var subject: UILabel!
}

As soon as I override the drawRect function like this...

override func drawRect(rect: CGRect) {
    self.layer.cornerRadius = 4
}

I get a strange border/shadow on the top and right of each cell (background colour set in storyboard)...

Note that even if I take out the self.layer.cornerRadius line, the borders still appear, so presumably I've missed something out at the drawRect function - I'm just not sure what.

What makes this especially peculiar, is that when I run the code on a iPhone 6+ or wider device, the problem goes away.

The only other (presumably) relevant code, is that which I use to size the cells appropriately in the view controller:

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    let size = collectionView.frame.width
    return CGSize(width: (size/3)-8, height: (size/3)-8)
}

What is the grey border/shadow, and how can I get rid of it? Many thanks in advance!

Answer 1

I suspect this is probably just an implementation quirk that appears because you're not quite doing things the way Apple wants. Unless you're subclassing UIView , you should call super.drawRect() in your own drawRect() method. Furthermore, drawRect() isn't really the right place to set cornerRadius : you should set that once, perhaps when the cell is created, then forget about it.

You might find Apple's reference for UIView and drawRect useful:

If you subclass UIView directly, your implementation of this method does not need to call super. However, if you are subclassing a different view class, you should call super at some point in your implementation.

One more thing: if you can avoid overriding drawRect() you should; it does have a performance impact.

Answer 2

I can only suggest to make a little hack: Adding this lines to drawRect

        self.layer.borderWidth = 1
        self.layer.borderColor = COLOR_OF_GRPUP_CELL