Deleting all HKQuantitySamples - ios

Question

I want to delete all HKQuantitySamples that my app has saved in the Health App for a certain HKQuantityType, how would I do that?
I can see the function
deleteObject:withCompletion:
in the Apple Documentation, but I do not really understand how to use it. Can somebody show an example maybe?
EDIT: I now use the following code for deleting:
I have saved my food information as a HKCorrelation and set my Local Food ID in the Correlations metadata HKMetadataKeyExternalUUID key.
For deletion I am fetching all the HKCorrelation objects between startDate and endDate and then if one of these fetched objects matches the Local Food ID I am looking for:
- I delete every object in that Correlation,
- Followed by deleting the Correlation itself
HKCorrelationType *foodType = [HKObjectType correlationTypeForIdentifier:HKCorrelationTypeIdentifierFood];
NSPredicate *predicate = [HKQuery predicateForSamplesWithStartDate:startDate endDate:endDate options:HKQueryOptionNone];
HKSampleQuery *query = [[HKSampleQuery alloc] initWithSampleType:foodType predicate:predicate limit:HKObjectQueryNoLimit sortDescriptors:nil resultsHandler:^(HKSampleQuery *query, NSArray *results, NSError *error) {
if (!results) {
NSLog(#"An error occured fetching the user's tracked food. In your app, try to handle this gracefully. The error was: %#.", error);
return;
}
dispatch_async(dispatch_get_main_queue(), ^{
for (HKCorrelation *foodCorrelation in results) {
if([[foodCorrelation.metadata valueForKey:HKMetadataKeyExternalUUID] isEqualToString:food_id_I_want_to_delete]) {
NSSet *objs = foodCorrelation.objects;
for (HKQuantitySample *sample in objs) {
[self.healthStore deleteObject:sample withCompletion:^(BOOL success, NSError *error) {
if (success) {
NSLog(#"Success. delete sample");
}
else {
NSLog(#"delete: An error occured deleting the sample. In your app, try to handle this gracefully. The error was: %#.", error);
}
}];
}
[self.healthStore deleteObject:foodCorrelation withCompletion:^(BOOL success, NSError *error) {
if (success) {
NSLog(#"Success. delete %#", [foodCorrelation.metadata valueForKey:HKMetadataKeyExternalUUID]);
}
else {
NSLog(#"delete: An error occured deleting the Correlation. In your app, try to handle this gracefully. The error was: %#.", error);
}
}];
return;
}
}
});
}];
[self.healthStore executeQuery:query];