Loading/Downloading image from URL on Swift

Question

I'd like to load an image from a URL in my application, so I first tried with Objective-C and it worked, however, with Swift, I've a compilation error:

'imageWithData' is unavailable: use object construction 'UIImage(data:)'

My function:

@IBOutlet var imageView : UIImageView

override func viewDidLoad() {
    super.viewDidLoad()

    var url:NSURL = NSURL.URLWithString("http://myURL/ios8.png")
    var data:NSData = NSData.dataWithContentsOfURL(url, options: nil, error: nil)

    imageView.image = UIImage.imageWithData(data)// Error here
}

In Objective-C:

- (void)viewDidLoad {
    [super viewDidLoad];

    NSURL *url = [NSURL URLWithString:(@"http://myURL/ios8.png")];
    NSData *data = [NSData dataWithContentsOfURL:url];

    _imageView.image = [UIImage imageWithData: data];
    _labelURL.text = @"http://www.quentinroussat.fr/assets/img/iOS%20icon's%20Style/ios8.png";
 }

Can someone please explain me why the imageWithData: doesn't work with Swift, and how can I solve the problem.

Answer 1

Swift 2.x answer that downloads image to file (as opposed to Leo Dabus's answer, which stores the image in memory). Based on Leo Dabus's answer and Rob's answer from Get the data from NSURLSession DownloadTaskWithRequest from completion handler:

    // Set download vars
    let downloadURL = NSURL() // URL to download from
    let localFilename = "foobar.png" // Filename for storing locally 

    // Create download request
    let task = NSURLSession.sharedSession().downloadTaskWithURL(downloadURL) { location, response, error in
        guard location != nil && error == nil else {
            print("Error downloading message: \(error)")
            return
        }

        // If here, no errors so save message to permanent location
        let fileManager = NSFileManager.defaultManager()
        do {
            let documents = try fileManager.URLForDirectory(.DocumentDirectory, inDomain: .UserDomainMask, appropriateForURL: nil, create: false)
            let fileURL = documents.URLByAppendingPathComponent(localFilename)
            try fileManager.moveItemAtURL(location!, toURL: fileURL)
            self.doFileDownloaded(fileURL, localFilename: localFilename)
            print("Downloaded message @ \(localFilename)")
        } catch {
            print("Error downloading message: \(error)")
        }
    }

    // Start download
    print("Starting download @ \(downloadURL)")
    task.resume()


// Helper function called after file successfully downloaded
private func doFileDownloaded(fileURL: NSURL, localFilename: String) {

    // Do stuff with downloaded image

}

Answer 2

Swift 4::

This will shows loader while loading the image. You can use NSCache which store image temporarily

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()
    }
}

Usage:-

truckImageView.loadImageUsingCache(withUrl: currentTruck.logoString)

Answer 3

If you just want to load image (Asynchronously!) - just add this small extension to your swift code:

extension UIImageView {
    public func imageFromUrl(urlString: String) {
        if let url = NSURL(string: urlString) {
            let request = NSURLRequest(URL: url)
            NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) {
                (response: NSURLResponse?, data: NSData?, error: NSError?) -> Void in
                if let imageData = data as NSData? {
                    self.image = UIImage(data: imageData)
                }
            }
        }
    }
}

And use it this way:

myImageView.imageFromUrl("https://robohash.org/123.png")

Answer 4

Swift 2 with error Handle and custom request header

Simply add extension to 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()
        }
    }
}

And then, use the new imageFromUrl(urlString: String) to download image

Usage:

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

Answer 5

Here is Working code for Loading / Downloading image from URL. NSCache automatically and Display Placeholder image before download and Load Actual image (Swift 4 Code).

func NKPlaceholderImage(image:UIImage?, imageView:UIImageView?,imgUrl:String,compate:@escaping (UIImage?) -> Void){

    if image != nil && imageView != nil {
        imageView!.image = image!
    }

    var urlcatch = imgUrl.replacingOccurrences(of: "/", with: "#")
    let documentpath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
    urlcatch = documentpath + "/" + "\(urlcatch)"

    let image = UIImage(contentsOfFile:urlcatch)
    if image != nil && imageView != nil
    {
        imageView!.image = image!
        compate(image)

    }else{

        if let url = URL(string: imgUrl){

            DispatchQueue.global(qos: .background).async {
                () -> Void in
                let imgdata = NSData(contentsOf: url)
                DispatchQueue.main.async {
                    () -> Void in
                    imgdata?.write(toFile: urlcatch, atomically: true)
                    let image = UIImage(contentsOfFile:urlcatch)
                    compate(image)
                    if image != nil  {
                        if imageView != nil  {
                            imageView!.image = image!
                        }
                    }
                }
            }
        }
    }
}

Use Like this :

// Here imgPicture = your imageView
// UIImage(named: "placeholder") is Display image brfore download and load actual image. 

NKPlaceholderImage(image: UIImage(named: "placeholder"), imageView: imgPicture, imgUrl: "Put Here your server image Url Sting") { (image) in }

Answer 6

Swift 2.2 || Xcode 7.3

I got Amazing results!! with AlamofireImage swift library

It provides multiple features like:

• Asynchronously download
• Auto Purging Image Cache if memory warnings happen for the app
• Image URL caching
• Image Caching
• Avoid Duplicate Downloads

and very easy to implement for your app

Step.1 Install pods

---

Alamofire 3.3.x

pod 'Alamofire'

AlamofireImage 2.4.x

pod 'AlamofireImage'

Step.2 import and Use

import Alamofire
import AlamofireImage

let downloadURL = NSURL(string: "http://cdn.sstatic.net/Sites/stackoverflow/company/Img/photos/big/6.jpg?v=f4b7c5fee820")!
imageView.af_setImageWithURL(downloadURL)

that's it!! it will take care everything

---

Great thanks to Alamofire guys, for making iDevelopers life easy ;)