iphone - Making http request in for loop fails in ios -

i doing lots of web request asynchronous call in loop 3 call success out of 10 call. when made synchronous success rate 100%. want asynchronously.please me. sample code following:

+(void)saveexpenceinbackground {  nsarray *array = [expense getsortedexpenseforuser:[coredatamanager sharedmanager].user forcontext:[coredatamanager sharedmanager].managedobjectcontext];  (expense *expence in array) {      nsdictionary *reqdict = [kzexpencedataandservicehandler convertobjecttodictionary:expence];      [expencedataandservicehandler expencesavetoserver:reqdict];   } }      +(void) expencesavetoserver:            requestdict :(nsdictionary *)reqdict                 { @try {      nsdata * jsondata = [nsjsonserialization datawithjsonobject:reqdict options:0 error:&error];      nsstring *datastring = [[nsstring alloc] initwithdata:jsondata encoding:nsutf8stringencoding];      nsstring *str = [nsstring stringwithformat:@"method=%@&data=%@",[postdict valueforkey:@"method"], datastring];      nsstring *webmethod = [self httpmethodtypeforservicetype:method];      nsmutableurlrequest *request = [[nsmutableurlrequest alloc] initwithurl:[nsurl urlwithstring:[[userpreference objectforkey:kzbaseurl] stringbyappendingstring:relativepath]]];      [request sethttpmethod:webmethod];     // [r setallhttpheaderfields:dictheaders];     [request sethttpbody:[str datausingencoding:nsutf8stringencoding]];//[inputparameter.dict_postparameters objectforkey:webservicejsondatapostdictkey]     [request settimeoutinterval:120];      [nsurlconnection sendasynchronousrequest:request queue:[nsoperationqueue mainqueue] completionhandler:^(nsurlresponse *response, nsdata *data, nserror *connectionerror) {         if (connectionerror)         {             return;         }          nsdictionary *responsedict = [btcwebservicehelper jsonvalidationwithdictionary:data];           if (responsedict != nil) {               nsmutabledictionary *dic = [responsedict mutablecopy];             [dic setobject:[reqdict valueforkey:@"expence_id"] forkey:@"expence_id"];             }      }];   } @catch (nsexception *exception) {     nslog(@"exception %@",exception); } @finally {  }   }   +(nsdictionary *)convertobjecttodictionary:(expense *)expence {  nsdictionary *requestdict = [@{@"receipt_key":expence.receipt_key,                                @"store_name": expence.store_name,                                @"amount": expence.amount,                                @"date_purchase": expence.date_purchase,                                @"is_processed":expence.is_processed?[nsnumber numberwithbool:no]:[nsnumber numberwithbool:yes],                                @"item_name":expence.item_name ,                                @"user_folder": expence.user_folder ,                                @"folder_name": expence.folder_name,                                @"category_id": expence.category_id,                                @"is_deleted": expence.is_deleted?[nsnumber numberwithbool:no]:[nsnumber numberwithbool:yes],                                @"is_approved": expence.is_approved?[nsnumber numberwithbool:no]:[nsnumber numberwithbool:yes],                                @"active_vat_percentage":![[nsstring stringwithformat:@"%@",expence.active_vat_percentage] isequal: @"nan"]?expence.active_vat_percentage:@"" ,                                @"vat_qualified": expence.vat_qualified?[nsnumber numberwithbool:no]:[nsnumber numberwithbool:yes],                                @"vat_percentage": ![[nsstring stringwithformat:@"%@",expence.vat_percentage] isequal: @"nan"]?expence.vat_percentage:@"",                                @"vat_amount": ![[nsstring stringwithformat:@"%@",expence.vat_amount] isequal: @"nan"]?expence.vat_amount:@"",                                @"net_expense": ![[nsstring stringwithformat:@"%@",expence.net_expense] isequal: @"nan"]?expence.net_expense:@"",                                @"is_fuel": expence.is_fuel?[nsnumber numberwithbool:no]:[nsnumber numberwithbool:yes],                                @"fuel_type": ![[nsstring stringwithformat:@"%@",expence.fuel_type] isequal: @"nan"]?expence.fuel_type:@"",                                @"fuel_quantity": ![[nsstring stringwithformat:@"%@",expence.fuel_quantity] isequal: @"nan"]?expence.fuel_quantity:@"",                                @"fuel_amount": ![[nsstring stringwithformat:@"%@",expence.fuel_amount] isequal: @"nan"]?expence.fuel_amount:@"",                                @"fuel_rate": ![[nsstring stringwithformat:@"%@",expence.fuel_rate] isequal: @"nan"]?expence.fuel_rate:@"",                                @"bank_account_id": ![[nsstring stringwithformat:@"%@",expence.bank_account_id] isequal: @"nan"]?expence.bank_account_id:@"",                                @"is_paid": expence.is_paid?[nsnumber numberwithbool:no]:[nsnumber numberwithbool:yes],                                @"project_id": ![[nsstring stringwithformat:@"%@",expence.project_id] isequal: @"nan"]?expence.project_id:@"",                                @"description": @"",                                @"payment_method": ![[nsstring stringwithformat:@"%@",expence.payment_method] isequal: @"nan"]?expence.payment_method:@"",                                @"currency_id": expence.currency_id,                                @"image_name": [nsstring stringwithformat:@"img%@",expence.receipt_key],                                @"receipt_format": expence.receipt_format?expence.receipt_format:@"",                                @"image_original": expence.image?expence.image:@"",                                @"is_synced": expence.is_synced?[nsnumber numberwithbool:no]:[nsnumber numberwithbool:yes],                                @"expence_id":expence.expence_id?expence.expence_id:@"0",                                @"receipt_uid":expence.receipt_uid?expence.receipt_uid:@"",                                @"image_name":expence.image_name?expence.image_name:@""                                 } mutablecopy];   return  requestdict;  }