iOS Programming Cookbook

How to do it...

To build a custom Operation class, perform the following steps:

1. In our Xcode project, add a new Swift file with a class, named ImageDownloader, which extends the Operation class:

2. In the ImageDownloader.swift file, add the following code:

      class ImageDownloader: Operation { 
          let imgURL: URL 
          var downloadedImage: UIImage? 
          init(imageURL: URL) { 
              self.imgURL = imageURL 
          } 
     
          override func main() { 
              if self.isCancelled { 
                  return 
              } 
         
              do{ 
                  let data = try Data(contentsOf: self.imgURL) 
                  if self.isCancelled { 
                      return 
                  } 
                  self.downloadedImage = UIImage(data: data) 
              } 
              catch{ 
                  print(error) 
              } 
          } 
      } 

3. Now, go back to ViewController.swift and add the following ...