Auto Layout: can't get the frame size of UICollectionViewCell subViews

Question

I have a custom UICollectionViewCell subclass (MyCell), its interface is setup in Interface Builder using Auto Layout. The cell has an image view and a label.

Now, when I configure the cell, I need to know the width and the height of the image view. Sounds pretty simple, but it looks like it's impossible.

In my view controller:

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    MyCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MyCell" forIndexPath:indexPath];
    cell.itemNumber = indexPath.item;
    return cell;
}

In my cell subclass I am using my property's setter to customize the cell:

- (void)setItemNumber:(NSInteger)itemNumber {
    _itemNumber = itemNumber;
    self.label.text = [NSString stringWithFormat:@"%i", self.itemNumber];

    // In my actual project I need to know the image view's width and hight to request an image
    // of the right size from a server. Sadly, the frame is always {{0, 0}, {0, 0}}
    // (same for the bounds)
    NSLog(@"%@", NSStringFromCGRect(self.myImageView.frame));
}

A full example project can be found at https://github.com/kevinrenskers/CollectionViewAutoLayoutTest.

So the problem is this: I need to know the image view's size because I need to ask a server to generate an image of the correct size. And the image view's size is {0,0}..

I've tried to do the customizing in the -layoutSubviews method too:

- (void)setItemNumber:(NSInteger)itemNumber {
    _itemNumber = itemNumber;
}

- (void)layoutSubviews {
    if (self.myImageView.frame.size.height) {
        self.label.text = [NSString stringWithFormat:@"%i", self.itemNumber];
        NSLog(@"%@", NSStringFromCGRect(self.myImageView.frame));
    }
}

Sadly, this is even more messed up. The method is called twice, first the frame is {{0, 0}, {0, 0}} and then the frame is set correctly. Thus the if statement that checks for the height. Once you start scrolling though, the wrong labels are showed for the wrong cells. I don't understand what's going on here.

The problem probably makes more sense when you try it in the example project.

Setting width- and height constraints and making IBOutlets to it sounds like a great option, but sadly the cells don't have a fixed size and the image needs to shrink and grow with the cell. Removing auto layout isn't an option either.

Answer 1

In the end I added top, right, bottom and left spacing constraints on the imageview (to the superview), added IBOutlets to them and used something like this:

CGFloat height = self.contentView.bounds.size.height - self.topConstraint.constant - self.bottomConstraint.constant;
CGFloat width = self.contentView.bounds.size.width - self.leftConstraint.constant - self.rightConstraint.constant;