我对daniel.gindi的代码做了一些修改

这就是你要做的一切。

+ (void)putView:(UIView*)view insideShadowWithColor:(UIColor*)color andBlur:         (CGFloat)blur andOffset:(CGSize)shadowOffset andOpacity:(CGFloat)shadowOpacity
{
    CGRect shadowFrame = view.frame;
    UIView * shadow = [[UIView alloc] initWithFrame:shadowFrame];
    shadow.backgroundColor = [UIColor redColor];
    shadow.userInteractionEnabled = YES; // Modify this if needed
    shadow.layer.shadowColor = color.CGColor;
    shadow.layer.shadowOffset = shadowOffset;
    shadow.layer.shadowRadius = blur;
    shadow.layer.cornerRadius = view.layer.cornerRadius;
    shadow.layer.masksToBounds = NO;
    shadow.clipsToBounds = NO;
    shadow.layer.shadowOpacity = shadowOpacity;
    [view.superview insertSubview:shadow belowSubview:view];
}

如果你因为圆角、子视图和masksToBounds而挣扎，那么尝试使用我的函数:

- (UIView*)putView:(UIView*)view insideShadowWithColor:(UIColor*)color andRadius:(CGFloat)shadowRadius andOffset:(CGSize)shadowOffset andOpacity:(CGFloat)shadowOpacity
{
    CGRect shadowFrame; // Modify this if needed
    shadowFrame.size.width = 0.f;
    shadowFrame.size.height = 0.f;
    shadowFrame.origin.x = 0.f;
    shadowFrame.origin.y = 0.f;
    UIView * shadow = [[UIView alloc] initWithFrame:shadowFrame];
    shadow.userInteractionEnabled = NO; // Modify this if needed
    shadow.layer.shadowColor = color.CGColor;
    shadow.layer.shadowOffset = shadowOffset;
    shadow.layer.shadowRadius = shadowRadius;
    shadow.layer.masksToBounds = NO;
    shadow.clipsToBounds = NO;
    shadow.layer.shadowOpacity = shadowOpacity;
    [view.superview insertSubview:shadow belowSubview:view];
    [shadow addSubview:view];
    return shadow;
}

在你的视图中调用它。无论你的视图是否有圆角，无论它的大小，它的形状-一个漂亮的阴影将被绘制出来。

只要保留函数的返回值，这样当你想要删除表时就可以引用它(或者例如使用insertSubview:aboveView:)

在swift 4中进行了测试

import UIKit

extension UIView {
    @IBInspectable var dropShadow: Bool {
        set{
            if newValue {
                layer.shadowColor = UIColor.black.cgColor
                layer.shadowOpacity = 0.4
                layer.shadowRadius = 1
                layer.shadowOffset = CGSize.zero
            } else {
                layer.shadowColor = UIColor.clear.cgColor
                layer.shadowOpacity = 0
                layer.shadowRadius = 0
                layer.shadowOffset = CGSize.zero
            }
        }
        get {
            return layer.shadowOpacity > 0
        }
    }
}

生产

如果你像这样在检查器中启用它:

它将添加用户定义的运行时属性，结果是:

(我之前添加了拐角半径= 8)

:)

Swift 3 & IBInspectable解决方案: 灵感来自Ade的解决方案

首先，创建一个UIView扩展:

//
//  UIView-Extension.swift
//  

import Foundation
import UIKit

@IBDesignable
extension UIView {
     // Shadow
     @IBInspectable var shadow: Bool {
          get {
               return layer.shadowOpacity > 0.0
          }
          set {
               if newValue == true {
                    self.addShadow()
               }
          }
     }

     fileprivate func addShadow(shadowColor: CGColor = UIColor.black.cgColor, shadowOffset: CGSize = CGSize(width: 3.0, height: 3.0), shadowOpacity: Float = 0.35, shadowRadius: CGFloat = 5.0) {
          let layer = self.layer
          layer.masksToBounds = false

          layer.shadowColor = shadowColor
          layer.shadowOffset = shadowOffset
          layer.shadowRadius = shadowRadius
          layer.shadowOpacity = shadowOpacity
          layer.shadowPath = UIBezierPath(roundedRect: layer.bounds, cornerRadius: layer.cornerRadius).cgPath

          let backgroundColor = self.backgroundColor?.cgColor
          self.backgroundColor = nil
          layer.backgroundColor =  backgroundColor
     }


     // Corner radius
     @IBInspectable var circle: Bool {
          get {
               return layer.cornerRadius == self.bounds.width*0.5
          }
          set {
               if newValue == true {
                    self.cornerRadius = self.bounds.width*0.5
               }
          }
     }

     @IBInspectable var cornerRadius: CGFloat {
          get {
               return self.layer.cornerRadius
          }

          set {
               self.layer.cornerRadius = newValue
          }
     }


     // Borders
     // Border width
     @IBInspectable
     public var borderWidth: CGFloat {
          set {
               layer.borderWidth = newValue
          }

          get {
               return layer.borderWidth
          }
     }

     // Border color
     @IBInspectable
     public var borderColor: UIColor? {
          set {
               layer.borderColor = newValue?.cgColor
          }

          get {
               if let borderColor = layer.borderColor {
                    return UIColor(cgColor: borderColor)
               }
               return nil
          }
     }
}

然后，在界面构建器中选择你的UIView，设置阴影ON和角半径，如下所示:

结果!

当为容器视图分配阴影路径时，我使用以下技巧解决了这个问题:

[UIBezierPath bezierPathWithRoundedRect:cell.bounds cornerRadius:12]

请注意，阴影的路径是一个圆角矩形，与单元格包含的背景具有相同的角半径:

//this is the border for the UIView that is added to a cell
cell.backgroundView.layer.cornerRadius = 12;
cell.backgroundView.layer.masksToBounds = YES;
cell.backgroundView.layer.borderColor = [UIColor darkGrayColor].CGColor;
cell.backgroundView.layer.borderWidth = 1;

//this is the shadow around the cell itself (cannot have round corners with borders and shadow, need to use two views
cell.layer.shadowRadius = 2;
cell.layer.cornerRadius = 12;
cell.layer.masksToBounds = NO;
[[cell layer] setShadowColor:[[UIColor darkGrayColor] CGColor]];

[[cell layer] setShadowOffset:CGSizeMake(0.0,0.0)];
[[cell layer] setShadowOpacity:1.0];

UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:cell.bounds cornerRadius:12];
[[cell layer] setShadowPath:[path CGPath]];

如果你不想像David c建议的那样改变你的nibs和视图层次结构，这个方法可以帮你。为你的UIImageView添加圆角和阴影只需使用这个方法，例如:

[Utils roundCornersForImageView:myImageView withCornerRadius:6.0 
andShadowOffset:2.0];

(!)出于性能原因，我不认为在像UITableView这样的东西中使用这段代码是个好主意，因为这段代码改变了视图层次结构。所以我会建议改变你的nib，并添加一个容器视图的阴影效果和使用戴维C.代码。

+ (void)roundCornersForImageView:(UIImageView *)imageView 
withCornerRadius:(float)cornerRadius andShadowOffset:(float)shadowOffset
{
    const float CORNER_RADIUS = cornerRadius;
    const float BORDER_WIDTH = 1.0; 
    const float SHADOW_OFFSET = shadowOffset;
    const float SHADOW_OPACITY = 0.8;
    const float SHADOW_RADIUS = 3.0;

    //Our old image now is just background image view with shadow
    UIImageView *backgroundImageView = imageView;
    UIView *superView = backgroundImageView.superview;

    //Make wider actual visible rect taking into account shadow
    //offset
    CGRect oldBackgroundFrame = backgroundImageView.frame;
    CGRect newBackgroundFrame = CGRectMake(oldBackgroundFrame.origin.x, oldBackgroundFrame.origin.y, oldBackgroundFrame.size.width + SHADOW_OFFSET, oldBackgroundFrame.size.height + SHADOW_OFFSET);
    [backgroundImageView removeFromSuperview];
    backgroundImageView.frame = newBackgroundFrame;        

    //Make new UIImageView with rounded corners and put our old image
    CGRect frameForRoundedImageView = CGRectMake(0, 0, oldBackgroundFrame.size.width, oldBackgroundFrame.size.height);
    UIImageView *roundedImageView = [[UIImageView alloc]initWithFrame:frameForRoundedImageView];
    roundedImageView.image = imageView.image;
    [roundedImageView.layer setCornerRadius:CORNER_RADIUS];
    [roundedImageView.layer setBorderColor:[UIColor lightGrayColor].CGColor];        
    [roundedImageView.layer setBorderWidth:BORDER_WIDTH]; 
    [roundedImageView.layer setMasksToBounds:YES];

    //Set shadow preferences
    [backgroundImageView setImage:nil];
    [backgroundImageView.layer setShadowColor:[UIColor blackColor].CGColor];
    [backgroundImageView.layer setShadowOpacity:SHADOW_OPACITY];
    [backgroundImageView.layer setShadowRadius:SHADOW_RADIUS];
    [backgroundImageView.layer setShadowOffset:CGSizeMake(SHADOW_OFFSET, SHADOW_OFFSET)];   

    //Add out two image views back to the view hierarchy.
    [backgroundImageView addSubview:roundedImageView];
    [superView addSubview:backgroundImageView];   
}