iOS UIView性能最優的設計圓角而且繪製邊框顏色

//以給cell切圓角爲例
- (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
{
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.frame = CGRectMake(0, 0, cellWidth, cellHeight);

    CAShapeLayer *borderLayer = [CAShapeLayer layer];
    borderLayer.frame = CGRectMake(0, 0, cellWidth, cellHeight);
    borderLayer.lineWidth = 1.f;
    borderLayer.strokeColor = lineColor.CGColor;
    borderLayer.fillColor = [UIColor clearColor].CGColor;

    UIBezierPath *bezierPath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, cellWidth, cellHeight) cornerRadius:cornerRadius];
    maskLayer.path = bezierPath.CGPath;
    borderLayer.path = bezierPath.CGPath;

    [cell.contentView.layer insertSublayer:borderLayer atIndex:0];
    [cell.contentView.layer setMask:maskLayer];
}