Watch os 2.0 beta: access heart beat rate

Question

With Watch OS 2.0 developers are supposed to be allowed to access heart beat sensors.... I would love to play a bit with it and build a simple prototype for an idea I have,

Answer 1

You can get heart rate data by starting a workout and query heart rate data from healthkit.

Ask for premission for reading workout data.

HKHealthStore *healthStore = [[HKHealthStore alloc] init];
HKQuantityType *type = [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierHeartRate];
HKQuantityType *type2 = [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierDistanceWalkingRunning];
HKQuantityType *type3 = [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierActiveEnergyBurned];

[healthStore requestAuthorizationToShareTypes:nil readTypes:[NSSet setWithObjects:type, type2, type3, nil] completion:^(BOOL success, NSError * _Nullable error) {

    if (success) {
        NSLog(@"health data request success");

    }else{
        NSLog(@"error %@", error);
    }
}];

In AppDelegate on iPhone, respond this this request

-(void)applicationShouldRequestHealthAuthorization:(UIApplication *)application{

[healthStore handleAuthorizationForExtensionWithCompletion:^(BOOL success, NSError * _Nullable error) {
    if (success) {
        NSLog(@"phone recieved health kit request");
    }
}];
}

Then implement Healthkit Delegate:

-(void)workoutSession:(HKWorkoutSession *)workoutSession didFailWithError:(NSError *)error{

NSLog(@"session error %@", error);
}

-(void)workoutSession:(HKWorkoutSession *)workoutSession didChangeToState:(HKWorkoutSessionState)toState fromState:(HKWorkoutSessionState)fromState date:(NSDate *)date{

dispatch_async(dispatch_get_main_queue(), ^{
switch (toState) {
    case HKWorkoutSessionStateRunning:

        //When workout state is running, we will excute updateHeartbeat
        [self updateHeartbeat:date];
        NSLog(@"started workout");
    break;

    default:
    break;
}
});
}

Now it's time to write [self updateHeartbeat:date]

-(void)updateHeartbeat:(NSDate *)startDate{

__weak typeof(self) weakSelf = self;

//first, create a predicate and set the endDate and option to nil/none 
NSPredicate *Predicate = [HKQuery predicateForSamplesWithStartDate:startDate endDate:nil options:HKQueryOptionNone];

//Then we create a sample type which is HKQuantityTypeIdentifierHeartRate
HKSampleType *object = [HKSampleType quantityTypeForIdentifier:HKQuantityTypeIdentifierHeartRate];

//ok, now, create a HKAnchoredObjectQuery with all the mess that we just created.
heartQuery = [[HKAnchoredObjectQuery alloc] initWithType:object predicate:Predicate anchor:0 limit:0 resultsHandler:^(HKAnchoredObjectQuery *query, NSArray *sampleObjects, NSArray *deletedObjects, HKQueryAnchor *newAnchor, NSError *error) {

if (!error && sampleObjects.count > 0) {
    HKQuantitySample *sample = (HKQuantitySample *)[sampleObjects objectAtIndex:0];
    HKQuantity *quantity = sample.quantity;
    NSLog(@"%f", [quantity doubleValueForUnit:[HKUnit unitFromString:@"count/min"]]);
}else{
    NSLog(@"query %@", error);
}

}];

//wait, it's not over yet, this is the update handler
[heartQuery setUpdateHandler:^(HKAnchoredObjectQuery *query, NSArray *SampleArray, NSArray *deletedObjects, HKQueryAnchor *Anchor, NSError *error) {

 if (!error && SampleArray.count > 0) {
    HKQuantitySample *sample = (HKQuantitySample *)[SampleArray objectAtIndex:0];
    HKQuantity *quantity = sample.quantity;
    NSLog(@"%f", [quantity doubleValueForUnit:[HKUnit unitFromString:@"count/min"]]);
 }else{
    NSLog(@"query %@", error);
 }
}];

//now excute query and wait for the result showing up in the log. Yeah!
[healthStore executeQuery:heartQuery];
}

You also have a turn on Healthkit in capbilities. Leave a comment below if you have any questions.