iOS UIView性能最优的设计圆角并且绘制边框颜色

//以给cell切圆角为例
- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
{
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.frame = CGRectMake(, , cellWidth, cellHeight);

    CAShapeLayer *borderLayer = [CAShapeLayer layer];
    borderLayer.frame = CGRectMake(, , cellWidth, cellHeight);
    borderLayer.lineWidth = .f;
    borderLayer.strokeColor = lineColor.CGColor;
    borderLayer.fillColor = [UIColor clearColor].CGColor;

    UIBezierPath *bezierPath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(, , cellWidth, cellHeight) cornerRadius:cornerRadius];
    maskLayer.path = bezierPath.CGPath;
    borderLayer.path = bezierPath.CGPath;

    [cell.contentView.layer insertSublayer:borderLayer atIndex:];
    [cell.contentView.layer setMask:maskLayer];
}