What's Currently the "Correct" Way to Set a Uiview's Corner Radius

Giving UIView rounded corners

Try this

#import <QuartzCore/QuartzCore.h> // not necessary for 10 years now  :)

...

view.layer.cornerRadius = 5;
view.layer.masksToBounds = true;

Note: If you are trying to apply rounded corners to a UIViewController's view, it should not be applied in the view controller's constructor, but rather in -viewDidLoad, after view is actually instantiated.

How to set cornerRadius for only top-left and top-right corner of a UIView?

Pay attention to the fact that if you have layout constraints attached to it, you must refresh this as follows in your UIView subclass:

override func layoutSubviews() {
    super.layoutSubviews()
    roundCorners(corners: [.topLeft, .topRight], radius: 3.0)
}

If you don't do that it won't show up.

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And to round corners, use the extension:

extension UIView {
   func roundCorners(corners: UIRectCorner, radius: CGFloat) {
        let path = UIBezierPath(roundedRect: bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
        let mask = CAShapeLayer()
        mask.path = path.cgPath
        layer.mask = mask
    }
}

---

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Additional view controller case: Whether you can't or wouldn't want to subclass a view, you can still round a view. Do it from its view controller by overriding the viewWillLayoutSubviews() function, as follows:

class MyVC: UIViewController {
    /// The view to round the top-left and top-right hand corners
    let theView: UIView = {
        let v = UIView(frame: CGRect(x: 10, y: 10, width: 200, height: 200))
        v.backgroundColor = .red
        return v
    }()
    
    override func loadView() {
        super.loadView()
        view.addSubview(theView)
    }
    
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()

        // Call the roundCorners() func right there.
        theView.roundCorners(corners: [.topLeft, .topRight], radius: 30)
    }
}

Rounded Corners only on Top of a UIView

You can do this by setting a mask on your view's layer:

CAShapeLayer * maskLayer = [CAShapeLayer layer];
maskLayer.path = [UIBezierPath bezierPathWithRoundedRect: self.bounds byRoundingCorners: UIRectCornerTopLeft | UIRectCornerTopRight cornerRadii: (CGSize){10.0, 10.}].CGPath;

self.layer.mask = maskLayer;

IMPORTANT: You should do this in your view's layoutSubviews() method, so the view has already been resized from the storyboard

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In Swift <= 1.2

let maskLayer = CAShapeLayer()
maskLayer.path = UIBezierPath(roundedRect: bounds, byRoundingCorners: .TopLeft | .TopRight, cornerRadii: CGSize(width: 10.0, height: 10.0)).CGPath

layer.mask = maskLayer

---

Swift 2.x

let maskLayer = CAShapeLayer()
maskLayer.path = UIBezierPath(roundedRect: bounds, byRoundingCorners: UIRectCorner.TopLeft.union(.TopRight), cornerRadii: CGSizeMake(10, 10)).CGPath
layer.mask = maskLayer

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Swift 3.x

let maskLayer = CAShapeLayer()
maskLayer.path = UIBezierPath(roundedRect: view.bounds, byRoundingCorners: [.topLeft, .topRight], cornerRadii: CGSize(width: 10, height: 10)).cgPath
layer.mask = maskLayer

How to set UIView mask with corner radius, border and shadow?

Heh, just half hour later I managed to find solution to my own problem:

let path = UIBezierPath(roundedRect: rect, byRoundingCorners: UIRectCorner.allCorners, cornerRadii: CGSize(width: radius, height: radius))

let frameLayer = CAShapeLayer()
frameLayer.path = path.cgPath
frameLayer.shadowPath = path.cgPath

frameLayer.lineWidth = borderWidth
frameLayer.strokeColor = borderColor.cgColor
frameLayer.fillColor = backgroundColor?.cgColor
frameLayer.shadowOffset = shadowOffset
frameLayer.shadowOpacity = shadowOpacity
frameLayer.shadowRadius = shadowRadius
frameLayer.shadowColor = shadowColor.cgColor

layer.mask = frameLayer
layer.insertSublayer(frameLayer, at: 0)

How to set corner radius of imageView?

Layer draws out of clip region, you need to set it to mask to bounds:

self.mainImageView.layer.masksToBounds = true

From the docs:

By default, the corner radius does not apply to the image in the
layer’s contents property; it applies only to the background color and
border of the layer. However, setting the masksToBounds property to
true causes the content to be clipped to the rounded corners

Different cornerRadius for each corner Swift 3 - iOS

You could set the default layer.cornerRadius to the smallest value and then set the layer mask's border to the bigger value.

let demoView = UIView(frame: CGRect(x: 100, y: 200, width: 100, height: 100))
demoView.backgroundColor = UIColor.red
demoView.layer.cornerRadius = 3.0

let maskPath = UIBezierPath(roundedRect: demoView.bounds,
                            byRoundingCorners: [.topLeft, .topRight, .bottomLeft],
                            cornerRadii: CGSize(width: 18.0, height: 0.0))

let maskLayer = CAShapeLayer()
maskLayer.path = maskPath.cgPath
demoView.layer.mask = maskLayer
view.addSubview(demoView)

Round two corners in UIView

CACornerMask introduced in iOS 11, which help to define topleft, topright, bottomleft, bottom right in view layer. Below is example to use.

Here I try to rounded only two top corner:

myView.clipsToBounds = true
myView.layer.cornerRadius = 10
myView.layer.maskedCorners = [.layerMinXMinYCorner,.layerMaxXMinYCorner]

FYI Ref:

UIView with shadow, rounded corners and custom drawRect

This is a tricky one. UIView's clipsToBounds is necessary to get the rounded corners. But CALayer's masksToBounds has to be false so the shadow is visible. Somehow, everything works if drawRect is not overridden, but actually it shouldn't.

The solution is to create a superview to provide the shadow (in the demonstration below this is the shadowView). You can test the following in Playground:

class MyView : UIView {
    override func drawRect(rect: CGRect) {
        let c = UIGraphicsGetCurrentContext()
        CGContextAddRect(c, CGRectMake(10, 10, 80, 80))
        CGContextSetStrokeColorWithColor(c , UIColor.redColor().CGColor)
        CGContextStrokePath(c)
    }
}

let superview = UIView(frame: CGRectMake(0, 0, 200, 200))

let shadowView = UIView(frame: CGRectMake(50, 50, 100, 100))
shadowView.layer.shadowColor = UIColor.blackColor().CGColor
shadowView.layer.shadowOffset = CGSizeZero
shadowView.layer.shadowOpacity = 0.5
shadowView.layer.shadowRadius = 5

let view = MyView(frame: shadowView.bounds)
view.backgroundColor = UIColor.whiteColor()
view.layer.cornerRadius = 10.0
view.layer.borderColor = UIColor.grayColor().CGColor
view.layer.borderWidth = 0.5
view.clipsToBounds = true

shadowView.addSubview(view)
superview.addSubview(shadowView)

Result:

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