iOS: load an image from url

Question

I need to load an image from a url and set it inside an UIImageView; the problem is that I don\'t know the exact size of the image, then how can I show the image correctly?<

Answer 1

IN SWIFT 3.0

The main thread must be always remain free so it serves the user interface and user interactions.

class ViewController: UIViewController {

@IBOutlet weak var imageView: UIImageView!

private func fetchImage() {
    let imageURL = URL(string: "https://i.stack.imgur.com/9z6nS.png")
    var image: UIImage?
    if let url = imageURL {
        //All network operations has to run on different thread(not on main thread).
        DispatchQueue.global(qos: .userInitiated).async {
            let imageData = NSData(contentsOf: url)
            //All UI operations has to run on main thread.
            DispatchQueue.main.async {
                if imageData != nil {
                    image = UIImage(data: imageData as! Data)
                    self.imageView.image = image
                    self.imageView.sizeToFit()
                } else {
                    image = nil
                }
            }
        }
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    fetchImage()
}

}