Question

I have an UICollectionView where I am reusing many UICollectionViewCells with product information, think of Pinterest.

But it comes to a point where I have a price tag and would like to rotate the price ribbon about 45 degrees for everyone of the cells.

What would be the best performance wise method to achieve that?

I have tried with:

#import <QuartzCore/QuartzCore.h>

@interface ItemCollectionViewCell : UICollectionViewCell

@property (weak, nonatomic) IBOutlet UILabel *price;

@end


@implementation ItemCollectionViewCell

@synthesize price;

- (void)awakeFromNib {
    price.layer.transform = CATransform3DMakeRotation(M_PI_4, 0, 0, 1);
    price.layer.transform = CATransform3DTranslate(price.transform, 25, -15, 0);
    price.layer.shouldRasterize = YES;
}

@end

But the overall result as scrolling and pushing new views into the navigation controller is really slow.

Update

• It seems that iOS6 Autolayout is the main cause for the performance decrease, but I still don’t know how to fix this or remove autolayout only for the price label.

Answer 1

What worked for me was to remove the attributes defined by iOS6 autoLayout feature inside the UICollectionViewCell where it sets constraints for the price label, being:

- (void)awakeFromNib {

    NSMutableArray* cons = [NSMutableArray array];
    //iterating through UICollectionViewCell constraint list
    for (NSLayoutConstraint* con in self.constraints) {
        //if the target constraint is `price` then add that to the array
        if (con.firstItem == price || con.secondItem == price) {
            [cons addObject:con];
        }
    }
    //remove the unwanted constraints array to the UICollectionViewCell
    [self removeConstraints:cons];

    //ready to roll…
    price.layer.transform = CATransform3DMakeRotation(M_PI_4, 0, 0, 1);
    price.layer.transform = CATransform3DTranslate(price.transform, 25, -15, 0);
    price.layer.shouldRasterize = YES;
}