How to make UICollectionViewFlowLayout itemSize dynamic for screen size

Question

I am working programmatically (no storyboard) and am having trouble making layout.itemSize dynamic for different screen sizes. I get this error message:

Answer 1

add following delegate method to your collection view

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
 {
UIImage *image;
long row = [indexPath row];

image = [UIImage imageNamed:_carImages[row]];

return image.size;
 }

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