view.layer.cornerRadius = 25
view.layer.masksToBounds = true

试试这个

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

...

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

注意:如果你试图将圆角应用到UIViewController的视图，它不应该应用在视图控制器的构造函数中，而应该应用在-viewDidLoad中，在视图实际实例化之后。

Swift 4 -使用IBDesignable

   @IBDesignable
    class DesignableView: UIView {
    }

    extension UIView
    {

        @IBInspectable
        var cornerRadius: CGFloat {
            get {
                return layer.cornerRadius
            }
            set {
            layer.cornerRadius = newValue
        }
    }
}

设置圆形视图的转角属性

设置masksToBounds布尔值，图像将不会在角半径边界外绘制

view.layer.cornerRadius = 5;

view.layer.masksToBounds = YES;

在Xcode 6上 你试一试

     self.layer.layer.cornerRadius = 5.0f;

or

    self.layer.layer.cornerRadius = 5.0f;
    self.layer.clipsToBounds = YES;

使用UIView扩展:

extension UIView {    

func addRoundedCornerToView(targetView : UIView?)
{
    //UIView Corner Radius
    targetView!.layer.cornerRadius = 5.0;
    targetView!.layer.masksToBounds = true

    //UIView Set up boarder
    targetView!.layer.borderColor = UIColor.yellowColor().CGColor;
    targetView!.layer.borderWidth = 3.0;

    //UIView Drop shadow
    targetView!.layer.shadowColor = UIColor.darkGrayColor().CGColor;
    targetView!.layer.shadowOffset = CGSizeMake(2.0, 2.0)
    targetView!.layer.shadowOpacity = 1.0
}
}

用法:

override func viewWillAppear(animated: Bool) {

sampleView.addRoundedCornerToView(statusBarView)

}