How to create rounded corners with CAShapeLayer - ios

Question

Is there a way to add rounded corners to a CAShapeLayer? In my case I needed the shape layer to create a dashed border via lineDashPattern.
^ notice how the dashed line is not rounded

Answer 1

The answer is simple. Create a bézier path with rounded corners.
UPDATE for Swift
view.clipsToBounds = true
view.layer.cornerRadius = 10.0
let border = CAShapeLayer()
border.path = UIBezierPath(roundedRect:view.bounds, cornerRadius:10.0).cgPath
border.frame = view.bounds
border.fillColor = nil
border.strokeColor = UIColor.purple.cgColor
border.lineWidth = borderWidth * 2.0 // doubled since half will be clipped
border.lineDashPattern = [15.0]
view.layer.addSublayer(border)
Objective-C
// (This old code assumes this is within a view with a custom property "border".)
self.clipsToBounds = YES;
self.layer.cornerRadius = 10.0;
self.border = [CAShapeLayer layer];
self.border.fillColor = nil;
self.border.path = [UIBezierPath bezierPathWithRoundedRect:self.bounds cornerRadius:10.0].cgPath;
self.border.frame = self.bounds;
self.border.strokeColor = [UIColor purpleColor].CGColor;
self.border.lineWidth = borderWidth * 2; // double desired width as half will be clipped
self.border.lineDashPattern = #[#15];
[self.layer addSublayer:self.border];

Answer 2

In swift 4 I created a UIView category (UIView+Borders) with the following function:
func borderDash(withRadius cornerRadius: Float, borderWidth: Float, borderColor: UIColor, dashSize: Int) {
let currentFrame = self.bounds
let shapeLayer = CAShapeLayer()
let path = CGMutablePath()
let radius = CGFloat(cornerRadius)
// Points - Eight points that define the round border. Each border is defined by two points.
let topLeftPoint = CGPoint(x: radius, y: 0)
let topRightPoint = CGPoint(x: currentFrame.size.width - radius, y: 0)
let middleRightTopPoint = CGPoint(x: currentFrame.size.width, y: radius)
let middleRightBottomPoint = CGPoint(x: currentFrame.size.width, y: currentFrame.size.height - radius)
let bottomRightPoint = CGPoint(x: currentFrame.size.width - radius, y: currentFrame.size.height)
let bottomLeftPoint = CGPoint(x: radius, y: currentFrame.size.height)
let middleLeftBottomPoint = CGPoint(x: 0, y: currentFrame.size.height - radius)
let middleLeftTopPoint = CGPoint(x: 0, y: radius)
// Points - Four points that are the center of the corners borders.
let cornerTopRightCenter = CGPoint(x: currentFrame.size.width - radius, y: radius)
let cornerBottomRightCenter = CGPoint(x: currentFrame.size.width - radius, y: currentFrame.size.height - radius)
let cornerBottomLeftCenter = CGPoint(x: radius, y: currentFrame.size.height - radius)
let cornerTopLeftCenter = CGPoint(x: radius, y: radius)
// Angles - The corner radius angles.
let topRightStartAngle = CGFloat(Double.pi * 3 / 2)
let topRightEndAngle = CGFloat(0)
let bottomRightStartAngle = CGFloat(0)
let bottmRightEndAngle = CGFloat(Double.pi / 2)
let bottomLeftStartAngle = CGFloat(Double.pi / 2)
let bottomLeftEndAngle = CGFloat(Double.pi)
let topLeftStartAngle = CGFloat(Double.pi)
let topLeftEndAngle = CGFloat(Double.pi * 3 / 2)
// Drawing a border around a view.
path.move(to: topLeftPoint)
path.addLine(to: topRightPoint)
path.addArc(center: cornerTopRightCenter,
radius: radius,
startAngle: topRightStartAngle,
endAngle: topRightEndAngle,
clockwise: false)
path.addLine(to: middleRightBottomPoint)
path.addArc(center: cornerBottomRightCenter,
radius: radius,
startAngle: bottomRightStartAngle,
endAngle: bottmRightEndAngle,
clockwise: false)
path.addLine(to: bottomLeftPoint)
path.addArc(center: cornerBottomLeftCenter,
radius: radius,
startAngle: bottomLeftStartAngle,
endAngle: bottomLeftEndAngle,
clockwise: false)
path.addLine(to: middleLeftTopPoint)
path.addArc(center: cornerTopLeftCenter,
radius: radius,
startAngle: topLeftStartAngle,
endAngle: topLeftEndAngle,
clockwise: false)
// Path is set as the shapeLayer object's path.
shapeLayer.path = path;
shapeLayer.backgroundColor = UIColor.clear.cgColor
shapeLayer.frame = currentFrame
shapeLayer.masksToBounds = false
shapeLayer.setValue(0, forKey: "isCircle")
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.strokeColor = borderColor.cgColor
shapeLayer.lineWidth = CGFloat(borderWidth)
shapeLayer.lineDashPattern = [NSNumber(value: dashSize), NSNumber(value: dashSize)]
shapeLayer.lineCap = kCALineCapRound
self.layer.addSublayer(shapeLayer)
self.layer.cornerRadius = radius;
}