Custom Closure in Swift for a Service Class

Hi Welcome all to this basic swift closures example

Now lets begin with the actual closure class

typealias CompletionBlock = ((NSData?) -> Void) //like typedef a completionBlockName or alais

class ServiceClass: AnyObject //The class is of type any object

{

    

   internal func makeServiceCall(urlToCall:String,completionHandler: CompletionBlock)

    {

        let googleURL:NSURL? = NSURL(string: urlToCall) //Can be nil

        

        

        let request:NSURLRequest = NSURLRequest(URL: googleURL!);

        

        let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { (data, response, error) -> Void in

            

            print("response is \(response)");

            print("response is \(error)");

            print("response is \(data)");

            

            if((error) == nil) //Could rather use if let here

            {

               completionHandler(nil);

            }

            else

            {

                if let finaldata = data

                {

                    completionHandler(finaldata);

                }

                else

                {

                    completionHandler(nil);

                }

            }

        }

        

        task.resume();

    }

}

How to invoke there methods are as follows.

    override func viewDidLoad() {

        super.viewDidLoad()

        

        ServiceClass().makeServiceCall("http://google.com") { (ServiceData) -> Void in

            

            if let _ = ServiceData

            {

                print("service data==\(ServiceData)")

            }

            else

            {

                print("service data is nil")

            }

        };

        // Do any additional setup after loading the view, typically from a nib.

    }