正如在这篇博文中所描述的，这里有一个方法来圆角的UIView:

+(void)roundView:(UIView *)view onCorner:(UIRectCorner)rectCorner radius:(float)radius
{
    UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:view.bounds
                                                   byRoundingCorners:rectCorner
                                                         cornerRadii:CGSizeMake(radius, radius)];
    CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
    maskLayer.frame = view.bounds;
    maskLayer.path = maskPath.CGPath;
    [view.layer setMask:maskLayer];
    [maskLayer release];
}

最酷的部分是你可以选择你想要四舍五入的角。

你可以使用下面的自定义UIView类，它也可以改变边框颜色和宽度。因为这是IBDesignalbe，你也可以在界面构建器中更改属性。

import UIKit

@IBDesignable public class RoundedView: UIView {

    @IBInspectable var borderColor: UIColor = UIColor.white {
        didSet {
            layer.borderColor = borderColor.cgColor
        }
    }

    @IBInspectable var borderWidth: CGFloat = 2.0 {
        didSet {
            layer.borderWidth = borderWidth
        }
    }

    @IBInspectable var cornerRadius: CGFloat = 0.0 {
        didSet {
            layer.cornerRadius = cornerRadius
        }
    }

}

现在你可以在UIView中使用一个快速的类别(代码如下图所示)，在@IBInspectable中显示在故事板上的结果(如果你正在使用类别，只使用拐角半径，而不是图层。cornerRadius作为关键路径。

extension UIView {
    @IBInspectable var cornerRadius: CGFloat {
        get {
            return layer.cornerRadius
        }
        set {
            layer.cornerRadius = newValue
            layer.masksToBounds = newValue > 0
        }
    }
}

如果圆角在viewDidload()中不起作用，最好在viewDidLayoutSubview()中编写代码

-(void)viewDidLayoutSubviews
{
    viewTextfield.layer.cornerRadius = 10.0 ;                                               
    viewTextfield.layer.borderWidth = 1.0f;
    viewTextfield.layer.masksToBounds =  YES;
    viewTextfield.layer.shadowRadius = 5;
    viewTextfield.layer.shadowOpacity = 0.3;
    viewTextfield.clipsToBounds = NO;
    viewTextfield.layer.shadowOffset = CGSizeMake(0.0f, 0.0f);
}

希望这能有所帮助!

在Swift 4.2和Xcode 10.1中

let myView = UIView()
myView.frame = CGRect(x: 200, y: 200, width: 200, height: 200)
myView.myViewCorners()
//myView.myViewCorners(width: myView.frame.width)//Pass View width
view.addSubview(myView)

extension UIView {
    //If you want only round corners
    func myViewCorners() {
        layer.cornerRadius = 10
        layer.borderWidth = 1.0
        layer.borderColor = UIColor.red.cgColor
        layer.masksToBounds = true
    }
    //If you want complete round shape, enable above comment line
    func myViewCorners(width:CGFloat) {
        layer.cornerRadius = width/2
        layer.borderWidth = 1.0
        layer.borderColor = UIColor.red.cgColor
        layer.masksToBounds = true
    }
}

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(20, 50, 200, 200)];

view.layer.backgroundColor = [UIColor whiteColor].CGColor;
view.layer.cornerRadius = 20.0;
view.layer.frame = CGRectInset(v.layer.frame, 20, 20);

view.layer.shadowOffset = CGSizeMake(1, 0);
view.layer.shadowColor = [[UIColor blackColor] CGColor];
view.layer.shadowRadius = 5;
view.layer.shadowOpacity = .25;

[self.view addSubview:view];
[view release];