Swift 4.1我创建了一个函数，只是传递图像url，图像生成后缓存键设置为完成块。

   class NetworkManager: NSObject {
  
  private var imageQueue = OperationQueue()
  private var imageCache = NSCache<AnyObject, AnyObject>()
  
  func downloadImageWithUrl(imageUrl: String, cacheKey: String, completionBlock: @escaping (_ image: UIImage?)-> Void) {
    
    let downloadedImage = imageCache.object(forKey: cacheKey as AnyObject)
    if let  _ = downloadedImage as? UIImage {
      completionBlock(downloadedImage as? UIImage)
    } else {
      let blockOperation = BlockOperation()
      blockOperation.addExecutionBlock({
        let url = URL(string: imageUrl)
        do {
          let data = try Data(contentsOf: url!)
          let newImage = UIImage(data: data)
          if newImage != nil {
            self.imageCache.setObject(newImage!, forKey: cacheKey as AnyObject)
            self.runOnMainThread {
              completionBlock(newImage)
            }
          } else {
            completionBlock(nil)
          }
        } catch {
          completionBlock(nil)
        }
      })
      self.imageQueue.addOperation(blockOperation)
      blockOperation.completionBlock = {
        print("Image downloaded \(cacheKey)")
      }
    }
  }
}
extension NetworkManager {
  fileprivate func runOnMainThread(block:@escaping ()->Void) {
    if Thread.isMainThread {
      block()
    } else {
      let mainQueue = OperationQueue.main
      mainQueue.addOperation({
        block()
      })
    }
  }
}

斯威夫特4::

这将在加载图像时显示加载器。 你可以使用NSCache临时存储图像

let imageCache = NSCache<NSString, UIImage>()
extension UIImageView {
    func loadImageUsingCache(withUrl urlString : String) {
        let url = URL(string: urlString)
        if url == nil {return}
        self.image = nil

        // check cached image
        if let cachedImage = imageCache.object(forKey: urlString as NSString)  {
            self.image = cachedImage
            return
        }

        let activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView.init(activityIndicatorStyle: .gray)
        addSubview(activityIndicator)
        activityIndicator.startAnimating()
        activityIndicator.center = self.center

        // if not, download image from url
        URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in
            if error != nil {
                print(error!)
                return
            }

            DispatchQueue.main.async {
                if let image = UIImage(data: data!) {
                    imageCache.setObject(image, forKey: urlString as NSString)
                    self.image = image
                    activityIndicator.removeFromSuperview()
                }
            }

        }).resume()
    }
}

用法:-

truckImageView.loadImageUsingCache(withUrl: currentTruck.logoString)

(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

Swift 2带有错误句柄和自定义请求头

简单地添加扩展到UIImageView:

extension UIImageView {
    public func imageFromUrl(urlString: String) {
        if let url = NSURL(string: urlString) {
            let request = NSMutableURLRequest(URL: url)
            request.setValue("<YOUR_HEADER_VALUE>", forHTTPHeaderField: "<YOUR_HEADER_KEY>")
            NSURLSession.sharedSession().dataTaskWithRequest(request) {
                (data, response, error) in
                guard let data = data where error == nil else{
                    NSLog("Image download error: \(error)")
                    return
                }

                if let httpResponse = response as? NSHTTPURLResponse{
                    if httpResponse.statusCode > 400 {
                        let errorMsg = NSString(data: data, encoding: NSUTF8StringEncoding)
                        NSLog("Image download error, statusCode: \(httpResponse.statusCode), error: \(errorMsg!)")
                        return
                    }
                }

            dispatch_async(dispatch_get_main_queue(), {
                NSLog("Image download success")
                self.image = UIImage(data: data)
            })
            }.resume()
        }
    }
}

然后，使用新的imageFromUrl(urlString: String)下载图像

用法:

imageView.imageFromUrl("https://i.imgur.com/ONaprQV.png")

使用Ascyimageview，你可以很容易地加载imageurl在imageview。

let image1Url：URL = URL（string： “（imageurl）” as String）！ imageview.imageURL=image1Url

斯威夫特5

extension UIImageView {
    func load(url: URL) {
        DispatchQueue.global().async { [weak self] in
            if let data = try? Data(contentsOf: url) {
                if let image = UIImage(data: data) {
                    DispatchQueue.main.async {
                        self?.image = image
                    }
                }
            }
        }
    }
}

使用

override func awakeFromNib() {
    super.awakeFromNib()
   if let url = URL(string:"<imageURLHere>"){
     imgView.load(url: url)
   }
}