如何在iPhone 6和iPhone 6plus的ios中删除Collection View Cell之间的空间？

- (CGSize)collectionView:(UICollectionView *)collectionView
                  layout:(UICollectionViewLayout *)collectionViewLayout
  sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    float width = collectionView.frame.size.width / 2;
    return CGSizeMake(width, width);

}

对于斯威夫特

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize
{
    return CGSizeMake(collectionView.frame.size.width/2, collectionView.frame.size.width/2)
}