どのような方法でも、次のようにすることができます。
プロジェクトに QuartzCore フレームワークを追加する
// .m ファイルにインポート
#import <QuartzCore/QuartzCore.h>
// このコードを実行
UIView *dd = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, 460)];
dd.backgroundColor = [UIColor redColor];
dd.layer.masksToBounds = YES;
dd.layer.borderColor = [UIColor whiteColor].CGColor;
[self.view addSubview:dd];
CGFloat cornerRadius = 0;
CGFloat borderWidth = 2;
UIColor *lineColor = [UIColor orangeColor];
CGRect maskRect = CGRectMake(100, 100, 200, 200);
//drawing
CGRect frame =maskRect;
CAShapeLayer *_shapeLayer = [CAShapeLayer layer];
//creating a path
CGMutablePathRef path = CGPathCreateMutable();
//drawing a border around a view
CGPathMoveToPoint(path, NULL, 0, frame.size.height - cornerRadius);
CGPathAddLineToPoint(path, NULL, 0, cornerRadius);
CGPathAddArc(path, NULL, cornerRadius, cornerRadius, cornerRadius, M_PI, -M_PI_2, NO);
CGPathAddLineToPoint(path, NULL, frame.size.width - cornerRadius, 0);
CGPathAddArc(path, NULL, frame.size.width - cornerRadius, cornerRadius, cornerRadius, -M_PI_2, 0, NO);
CGPathAddLineToPoint(path, NULL, frame.size.width, frame.size.height - cornerRadius);
CGPathAddArc(path, NULL, frame.size.width - cornerRadius, frame.size.height - cornerRadius, cornerRadius, 0, M_PI_2, NO);
CGPathAddLineToPoint(path, NULL, cornerRadius, frame.size.height);
CGPathAddArc(path, NULL, cornerRadius, frame.size.height - cornerRadius, cornerRadius, M_PI_2, M_PI, NO);
//path is set as the _shapeLayer object's path
_shapeLayer.path = path;
CGPathRelease(path);
_shapeLayer.backgroundColor = [[UIColor clearColor] CGColor];
_shapeLayer.frame = frame;
_shapeLayer.masksToBounds = NO;
_shapeLayer.fillColor = [[UIColor grayColor] CGColor];
_shapeLayer.strokeColor = [lineColor CGColor];
_shapeLayer.lineWidth = borderWidth;
//_shapeLayer is added as a sublayer of the view, the border is visible
[dd.layer addSublayer:_shapeLayer];
dd.layer.cornerRadius = cornerRadius;
うまくいくかもしれません。
幸せなコーディング。