Lots of free space between images

[firebird0001]

Lots of free space between images

[njdehoog]

The sample code you're showing here returns a random size, and thus a different size every time the prefferedSizeForItemAtIndexPath method is called. The prefferedSizeForItemAtIndexPath is called multiple times throughout the layout process and expects a consistent size to be returned for each index path.

If you want to test with random sizes you should store them in an array and implement the delegate method like this

return [[self.sizes objectAtIndex:indexPath.item] CGSizeValue];

Also make sure to set the contentMode on the cell's image view to aspect fill in this case.

[njdehoog]

I've replicated your example with this code and it works perfectly:

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (self) {

        _sizes = [NSMutableArray array];

        NSMutableArray *images = [[NSMutableArray alloc] init];
        for (int i = 1; i <= NUMBER_OF_IMAGES; i++) {
            NSString *imageName = [NSString stringWithFormat:@"photo-%02d.jpg", i];
            UIImage *image = [UIImage imageNamed:imageName];
            [images addObject:image];

            CGSize size = [image size];
            size.width += arc4random()%2000;
            size.height += arc4random()%2000;
            [_sizes addObject:[NSValue valueWithCGSize:size]];
        }
        _images = [images copy];
    }

    return self;
}

#pragma mark - UICollectionViewFlowLayoutDelegate

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(NHBalancedFlowLayout *)collectionViewLayout preferredSizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return [[self.sizes objectAtIndex:indexPath.item] CGSizeValue];
}

[firebird0001]

Finally I found the problem - wrong constraints in my custom cell .xib, absolutely my fault.

This is a great control! Thank you for your time.