Example of using NSURLSession

api.swift

/// Used to interact with the 2k games server API, and upload images to the server
class APIOperations: NSObject, NSURLSessionDelegate {


/** This method is using just a genereic URLSession to upload image to a server
    - Parameters:
        - Image: image to upload
        - imageType: kind of image (2k type) don't confuse it with png/jpg
        - callback: callback that contains information about successful or failed operation
    
*/
    static func uploadImage(image:UIImage,token:String, imageType:String, callback:((message:String?, error:String?)->Void))->NSURLSessionTask{
        

            var imageData = UIImagePNGRepresentation(image)
            imageData = NSData(data: imageData)
        
            var request = NSMutableURLRequest(URL: NSURL(string:APIKeys.url.rawValue)!)
            request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringLocalAndRemoteCacheData

//            var session = NSURLSession.sharedSession()
            var sessionConfig = NSURLSessionConfiguration.defaultSessionConfiguration()
            var authorizationString = "\(APIKeys.kUsername.rawValue):\(APIKeys.kPassword.rawValue)"
        
            var authorizationData = authorizationString.dataUsingEncoding(NSUTF8StringEncoding)
        
            //Authorization header
        
            var authHeader = "Basic \(authorizationData)"
            var authHeaderData = authHeader.dataUsingEncoding(NSUTF8StringEncoding)
        
            sessionConfig.HTTPAdditionalHeaders = ["Authorization":authHeader]


            let delegate = SessionDelegate()

            var session = NSURLSession(configuration: sessionConfig, delegate: delegate, delegateQueue: NSOperationQueue.mainQueue())
        
            request.HTTPMethod = "POST"
            
            var boundary = NSString(format: "---------------------------14737809831466499882746641449")
            var contentType = NSString(format: "multipart/form-data; boundary=%@",boundary)
            //  println("Content Type \(contentType)")
            request.addValue(contentType as String, forHTTPHeaderField: "Content-Type")
            
            var body = NSMutableData.alloc()
            
            // Add
            body.appendData(NSString(format: "\r\n--%@\r\n",boundary).dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData(NSString(format:"Content-Disposition: form-data; name=\"add\"\r\n\r\n").dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData("Test".dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!)

            // Image Type
            body.appendData(NSString(format: "\r\n--%@\r\n",boundary).dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData(NSString(format:"Content-Disposition: form-data; name=\"content_type\"\r\n\r\n").dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData(imageType.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!)

            // Token
            body.appendData(NSString(format: "\r\n--%@\r\n",boundary).dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData(NSString(format:"Content-Disposition: form-data; name=\"tok\"\r\n\r\n").dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData(token.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!)
 
            //Other fields
        
            // Image Content-Transfer-Encoding: binary
            body.appendData(NSString(format: "\r\n--%@\r\n", boundary).dataUsingEncoding(NSUTF8StringEncoding)!)


            body.appendData(NSString(format:"Content-Disposition: form-data; name=\"image\"; filename=\"img\(NSDate()).png\"\r\n").dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData(NSString(format: "Content-Type: image/png\r\n\r\n").dataUsingEncoding(NSUTF8StringEncoding)!)
            body.appendData(imageData)
           
                
            body.appendData(NSString(format: "\r\n--%@\r\n", boundary).dataUsingEncoding(NSUTF8StringEncoding)!)
            request.HTTPBody = body
        
        
            //  session.uploadTaskWithRequest(request, fromData: body)
           // NSURLSessionUploadTask()
            let task = session.uploadTaskWithRequest(request, fromData: body, completionHandler: { (data, response, error) -> Void in
                  var returnString:String?
                if let data = data, string = NSString(data: data, encoding: NSUTF8StringEncoding) {
                    returnString = string as String
                }
                
                var errorText:String?
                if let error = error{
                    errorText = error.description
                }
                
                callback(message: returnString, error: errorText)
                

                })
            task.resume()
       
        return task
    }
}

/// Used to deal with the 2k server authentication challenge
class SessionDelegate: NSObject, NSURLSessionDelegate{

   
    func URLSession(session: NSURLSession, didReceiveChallenge challenge: NSURLAuthenticationChallenge, completionHandler: (NSURLSessionAuthChallengeDisposition, NSURLCredential!) -> Void)
    {
      let credentials =   NSURLCredential(user: APIKeys.kUsername.rawValue, password: APIKeys.kPassword.rawValue, persistence: NSURLCredentialPersistence.Permanent)
        
        if challenge.previousFailureCount > 0 {
                println("Failure count: \(challenge.previousFailureCount)")
        }
        completionHandler(NSURLSessionAuthChallengeDisposition.UseCredential, credentials)
    }
    
    func URLSession(session: NSURLSession!, task: NSURLSessionTask!, didReceiveChallenge challenge: NSURLAuthenticationChallenge!, completionHandler: ((NSURLSessionAuthChallengeDisposition, NSURLCredential!) -> Void)!){
        
        println("task-didReceiveChallenge")
        
        if challenge.previousFailureCount > 0 {
            println("Alert Please check the credential")
            completionHandler(NSURLSessionAuthChallengeDisposition.CancelAuthenticationChallenge, nil)
        } else {
            
            let credentials =   NSURLCredential(user: APIKeys.kUsername.rawValue, password: APIKeys.kPassword.rawValue, persistence: NSURLCredentialPersistence.Permanent)
            completionHandler(NSURLSessionAuthChallengeDisposition.UseCredential,credentials)
        }
    }
}