ios - How do I get my Activity Indicator to start at the right time? -

from read can activate with button put right after button action starts http post , upload, right starts spinning right after function has finished, after upload complete, opposite of expect.
i'm new swift please explain answer nubie. many thanks.

@ibaction func upload(sender: anyobject) {      myactivityindicator.startanimating()      var imagedata = uiimagepngrepresentation(myimageview.image)      if imagedata != nil{         var request = nsmutableurlrequest(url: nsurl(string:"http://www.example.com/upload.php")!)          var session = nsurlsession.sharedsession()          request.httpmethod = "post"          var boundary = nsstring(format: "---------------------------14737809831466499882746641449")         var contenttype = nsstring(format: "multipart/form-data; boundary=%@",boundary)         //  println("content type \(contenttype)")         request.addvalue(contenttype, forhttpheaderfield: "content-type")          var body = nsmutabledata.alloc()          // title         body.appenddata(nsstring(format: "\r\n--%@\r\n",boundary).datausingencoding(nsutf8stringencoding)!)         body.appenddata(nsstring(format:"content-disposition: form-data; name=\"title\"\r\n\r\n").datausingencoding(nsutf8stringencoding)!)         body.appenddata("hello world".datausingencoding(nsutf8stringencoding, allowlossyconversion: true)!)          // image         body.appenddata(nsstring(format: "\r\n--%@\r\n", boundary).datausingencoding(nsutf8stringencoding)!)         body.appenddata(nsstring(format:"content-disposition: form-data; name=\"profile_img\"; filename=\"img.jpg\"\r\n").datausingencoding(nsutf8stringencoding)!)         //           println("body=\(body)")         body.appenddata(nsstring(format: "content-type: application/octet-stream\r\n\r\n").datausingencoding(nsutf8stringencoding)!)         body.appenddata(imagedata)         body.appenddata(nsstring(format: "\r\n--%@\r\n", boundary).datausingencoding(nsutf8stringencoding)!)            request.httpbody = body           var returndata = nsurlconnection.sendsynchronousrequest(request, returningresponse: nil, error: nil)          var returnstring = nsstring(data: returndata!, encoding: nsutf8stringencoding)          println("returnstring \(returnstring)")          //self.myactivityindicator.stopanimating()         //self.myimageview.image = nil      }   } 

try this

myactivityindicator.startanimating()                   dispatch_async(dispatch_get_global_queue(int(qos_class_user_initiated.value), 0)) {             //do post code here or call post func             dispatch_async(dispatch_get_main_queue()) {                 myactivityindicator.stopanimating()             }     } 

http://ijoshsmith.com/2014/07/29/a-swift-app-that-calls-json-web-services/ http://www.raywenderlich.com/79149/grand-central-dispatch-tutorial-swift-part-1