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!

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。

请导入Quartzcore框架，然后你必须设置setMaskToBounds为TRUE，这是非常重要的一行。

然后:[[yourView layer] setCornerRadius:5.0f];

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
    }
}

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;

UIView* viewWithRoundedCornersSize(float cornerRadius,UIView * original)
{
    // Create a white border with defined width
    original.layer.borderColor = [UIColor yellowColor].CGColor;
    original.layer.borderWidth = 1.5;

    // Set image corner radius
    original.layer.cornerRadius =cornerRadius;

    // To enable corners to be "clipped"
    [original setClipsToBounds:YES];
    return original;
}