ios - AWSDynamoDB - empty task result -

task = [[task continuewithsuccessblock:^id(bftask *task) {              nslog(@"%@: profile identity : %@", nsstringfromselector(_cmd), cognitouid);         awsdynamodbobjectmapper *dynamodbobjectmapper = [awsdynamodbobjectmapper defaultdynamodbobjectmapper];       return [dynamodbobjectmapper load:[tplcognitouserdbo class] hashkey:cognitouid rangekey:nil];           }]continuewithblock:^id(bftask *task)         {             if (task.error) {                 nslog(@"%@: request failed. error: [%@]",nsstringfromselector(_cmd), task.error);             }             if (task.exception) {                 nslog(@"%@: request failed. exception: [%@]", nsstringfromselector(_cmd), task.exception);             }             if (task.result) {                  tplcognitouserdbo *cognitoprofile = task.result;                  if(cognitoprofile)                 {                     nslog(@"%@: user id %@ ::",nsstringfromselector(_cmd), [cognitoprofile tplhandle]);                     [useridfound setstring: [cognitoprofile tplhandle]];                  } else {                     nslog(@"%@: output has no records in it.", nsstringfromselector(_cmd));                 }              }          return nil;          }];  return task; 

gives me error

2015-08-24 22:41:21.539 myplan[9904:815677] -[awstask tplhandle]: unrecognized selector sent instance

2015-08-24 22:41:21.905 myplan[9904:815766] awsiossdkv2 [debug] awssignature.m line:320 | -[awssignaturev4signer signrequestv4:] | payload {"key":{"tplcognitoid":{"s":"some value here"}},"tablename":"tplcognitouser"}

2015-08-24 22:41:22.341 myplan[9904:815766] awsiossdkv2 [verbose] awsurlresponseserialization.m line:79 | -[awsjsonresponseserializer responseobjectforresponse:originalrequest:currentrequest:data:error:] | response body: [{}]

** db definition

@interface tplcognitouserdbo :  awsdynamodbobjectmodel <awsdynamodbmodeling>  //keys  @property (nonatomic, strong) nsstring *tplcognitoid;  //other attributes  @property (nonatomic, strong) nsstring *tplhandle; 

the test result shown type, code continuewithblock:^id(bftask *task). task type not matched in code. – yi zhu