AWS S3 Swift – Download Image

In the example I will be downloading an image from my S3 bucket using S3TransferUtility for iOS in swift. You can find the source here on github

In the example i have 2 outlets:

    @IBOutlet weak var progressView: UIProgressView!
    @IBOutlet weak var imageView: UIImageView!

This function defines what s3 bucket we are using and the file/image we need to download. It then handles the progress view and finally the image view.

func downloadImage(){
        var completionHandler: AWSS3TransferUtilityDownloadCompletionHandlerBlock?

        //downloading image
        let S3BucketName: String = "yourBucketName"
        let S3DownloadKeyName: String = "example-image-1.png"

        let expression = AWSS3TransferUtilityDownloadExpression()
        expression.downloadProgress = {(task: AWSS3TransferUtilityTask, bytesSent: Int64, totalBytesSent: Int64, totalBytesExpectedToSend: Int64) in
            dispatch_async(dispatch_get_main_queue(), {
                let progress = Float(totalBytesSent) / Float(totalBytesExpectedToSend)
                self.progressView.progress = progress
                //   self.statusLabel.text = "Downloading..."
                NSLog("Progress is: %f",progress)
        self.completionHandler = { (task, location, data, error) -> Void in
            dispatch_async(dispatch_get_main_queue(), {
                if ((error) != nil){
                    NSLog("Failed with error")
                    NSLog("Error: %@",error!);
                    //   self.statusLabel.text = "Failed"
                else if(self.progressView.progress != 1.0) {
                    //    self.statusLabel.text = "Failed"
                    NSLog("Error: Failed - Likely due to invalid region / filename")
                    //    self.statusLabel.text = "Success"
                    self.imageView.image = UIImage(data: data!)
        let transferUtility = AWSS3TransferUtility.defaultS3TransferUtility()
        transferUtility?.downloadToURL(nil, bucket: S3BucketName, key: S3DownloadKeyName, expression: expression, completionHander: completionHandler).continueWithBlock { (task) -> AnyObject! in
            if let error = task.error {
                NSLog("Error: %@",error.localizedDescription);
                //  self.statusLabel.text = "Failed"
            if let exception = task.exception {
                NSLog("Exception: %@",exception.description);
                //  self.statusLabel.text = "Failed"
            if let _ = task.result {
                //    self.statusLabel.text = "Starting Download"
                NSLog("Download Starting!")
                // Do something with uploadTask.
            return nil;

2 thoughts on “AWS S3 Swift – Download Image”

  1. Hi jzorz,
    I am getting this error pls help me, Nil is not compatible with expected argument type ‘NSURL’ near the line below

    -> transferUtility?.downloadToURL(nil, bucket: ……

    1. Hi Puneeth. Do you have var completionHandler: AWSS3TransferUtilityDownloadCompletionHandlerBlock? in your controller? I’ve added source files on github so you can quickly view how I did it. Github

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