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How to load a remote image URL into UIImageView

Paul Hudson       @twostraws

UIImageView is designed to load only local images, but with a little work you can make it load remote images too. To get a basic solution, add an extension to UIImageView that downloads image data using a GCD background thread, then converts that to a UIImage, and loads it back into the image view on the main thread:

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
                    }
                }
            }
        }
    }
}

Keep in mind that if you try to call that method several times on the same image view - e.g. if you’re scrolling through a table – then you’re going to hit problems, because multiple images will start downloading.

If you want that to work then you should subclass UIImageView so you can store the URL that was requested, and compare that URL inside the load() function to make sure it hasn’t been changed in the time between starting the fetch and loading the image. But if you’re that serious, I would suggest using something like SDWebImage instead: https://github.com/rs/SDWebImage.

Available from iOS 8.0

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