您可以使用pod SDWebImage来实现相同的功能。它很容易使用。你可以在SDWebImage这里获得文档

下面是示例代码

self.yourImage.sd_setImage(with: NSURL(string: StrUrl as String ) as URL!, placeholderImage: placeholderImage, options: SDWebImageOptions(rawValue: 0), completed: { (image, error, cacheType, imageURL) in
                if( error != nil)
                {
                    print("Error while displaying image" , (error?.localizedDescription)! as String)
                }
            })

let url = NSURL.URLWithString("http://live-wallpaper.net/iphone/img/app/i/p/iphone-4s-wallpapers-mobile-backgrounds-dark_2466f886de3472ef1fa968033f1da3e1_raw_1087fae1932cec8837695934b7eb1250_raw.jpg");
var err: NSError?
var imageData :NSData = NSData.dataWithContentsOfURL(url,options: NSDataReadingOptions.DataReadingMappedIfSafe, error: &err)
var bgImage = UIImage(data:imageData)

(Swift 4更新) 为了直接回答最初的问题，下面是发布的Objective-C代码片段的快速等效版本。

let url = URL(string: image.url)
let data = try? Data(contentsOf: url!) //make sure your image in this url does exist, otherwise unwrap in a if let check / try-catch
imageView.image = UIImage(data: data!)

免责声明:

需要注意的是，Data(contentsOf:)方法将在执行代码的同一线程中同步下载url的内容，因此不要在应用程序的主线程中调用此方法。

让相同的代码异步运行，而不阻塞UI的简单方法是使用GCD:

let url = URL(string: image.url)

DispatchQueue.global().async {
    let data = try? Data(contentsOf: url!) //make sure your image in this url does exist, otherwise unwrap in a if let check / try-catch
    DispatchQueue.main.async {
        imageView.image = UIImage(data: data!)
    }
}

也就是说，在现实生活中的应用程序中，如果您希望获得最佳的用户体验并避免同一映像的多次下载，您可能还希望不仅下载它们，而且缓存它们。已经有相当多的库可以无缝地做到这一点，而且它们都非常易于使用。我个人推荐翠鸟:

import Kingfisher

let url = URL(string: "url_of_your_image")
// this downloads the image asynchronously if it's not cached yet
imageView.kf.setImage(with: url) 

就是这样

一个快速的黑客，如果你想快速检查图像从url

 let imageURL = NSURL(string: "https://farm2.staticflickr.com/1591/26078338233_d1466b7da2_m.jpg")
 let imagedData = NSData(contentsOfURL: imageURL!)!
 imageView?.image = UIImage(data: imagedData)

我在一个tableview中实现了一个只有图像的自定义单元格

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell{
        
        let cell = tableView.dequeueReusableCellWithIdentifier("theCell", forIndexPath: indexPath) as! customTableViewCell

        let imageURL = NSURL(string: "https://farm2.staticflickr.com/1591/26078338233_d1466b7da2_m.jpg")
        
        let imagedData = NSData(contentsOfURL: imageURL!)!
            
        cell.imageView?.image = UIImage(data: imagedData)
        
        return cell
        
    }

翠鸟是一个最好的库加载图像到URL。

Github URL - https://github.com/onevcat/Kingfisher

// If you want to use Activity Indicator.
imageview_pic.kf.indicatorType = .activity
imageview_pic.kf.setImage(with: URL(string: "Give your url string"))

// If you want to use custom placeholder image.
imageview_pic.kf.setImage(with: URL(string: "Give your url string"), placeholder: UIImage(named: "placeholder image name"), options: nil, progressBlock: nil, completionHandler: nil)

对于Swift-3及以上版本:

extension UIImageView {
  public func imageFromUrl(urlString: String) {
    if let url = URL(string: urlString) {
        let request = URLRequest(url: url)
        NSURLConnection.sendAsynchronousRequest(request as URLRequest, queue: .main, completionHandler: { (response, data, error) in
            if let imageData = data as NSData? {
                self.image = UIImage(data: imageData as Data)
            }
        })
    }
  }
}