对于iOS healthkit如何保存收缩压和舒张压值？

这是在健康套件中保存血压数据的代码

 HKUnit *BPunit = [HKUnit millimeterOfMercuryUnit];
 HKQuantity *BPSysQuantity = [HKQuantity quantityWithUnit:BPunit doubleValue:150.0];
 HKQuantityType *BPSysType = [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierBloodPressureSystolic];
 HKQuantitySample *BPSysSample = [HKQuantitySample quantitySampleWithType:BPSysType quantity:BpsysQuantity startDate:now endDate:now];
 [self.healthStore saveObject:BPSysSample withCompletion:^(BOOL success, NSError *error) 

舒张压也同样如此，

但是如何将两者组合保存为健康应用程序中的单个条目？目前，健康应用程序中为收缩压和舒张压保存了两个不同的条目。

- (void)saveBloodPressureIntoHealthStore:(double)Systolic Dysbp:(double)Diastolic {

HKUnit *BloodPressureUnit = [HKUnit millimeterOfMercuryUnit];

HKQuantity *SystolicQuantity = [HKQuantity quantityWithUnit:BloodPressureUnit doubleValue:Systolic];
HKQuantity *DiastolicQuantity = [HKQuantity quantityWithUnit:BloodPressureUnit doubleValue:Diastolic];

HKQuantityType *SystolicType = [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierBloodPressureSystolic];
HKQuantityType *DiastolicType = [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierBloodPressureDiastolic];

NSDate *now = [NSDate date];

HKQuantitySample *SystolicSample = [HKQuantitySample quantitySampleWithType:SystolicType quantity:SystolicQuantity startDate:now endDate:now];
HKQuantitySample *DiastolicSample = [HKQuantitySample quantitySampleWithType:DiastolicType quantity:DiastolicQuantity startDate:now endDate:now];

NSSet *objects=[NSSet setWithObjects:SystolicSample,DiastolicSample, nil];
HKCorrelationType *bloodPressureType = [HKObjectType correlationTypeForIdentifier:
                                 HKCorrelationTypeIdentifierBloodPressure];
HKCorrelation *BloodPressure = [HKCorrelation correlationWithType:bloodPressureType startDate:now endDate:now objects:objects];
                                [self.healthStore saveObject:BloodPressure withCompletion:^(BOOL success, NSError *error) {
    if (!success) {
        NSLog(@"An error occured saving the height sample %@. In your app, try to handle this gracefully. The error was: %@.", BloodPressure, error);
        abort();
    }
    [_activity stopAnimating];
    UIAlertView *savealert=[[UIAlertView alloc]initWithTitle:@"HealthDemo" message:@"Blood Pressure values has been saved to Health App" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [savealert show];

}];
}