How to track a user's location and display the path travelled using Google Maps ios SDK

Question

I'm currently building an ios app and I'm hoping to implement a function where the user's location is displayed on a Google Map view and when they move a polyline show's the path that has been travelled by the user so far. This obviously needs to happen in realtime.

So far I've initialised a Google Maps view and can display the user's current location using the observeValueForKeyPath function. The view and location marker update as the user moves.

I figured the best way to do this would be to create a GMSMutablePath object that adds the user's current location every time the map camera updates to the new location and then create a polyline from that path. The code I've used for this is below:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"myLocation"] && [object isKindOfClass:[GMSMapView class]])
    {
        [self.myMapView animateToCameraPosition:[GMSCameraPosition cameraWithLatitude:self.myMapView.myLocation.coordinate.latitude
                                                                                 longitude:self.myMapView.myLocation.coordinate.longitude
                                                                                      zoom:18]];


        [trackedPath addCoordinate:CLLocationCoordinate2DMake(self.myMapView.myLocation.coordinate.latitude, self.myMapView.myLocation.coordinate.longitude)];
        GMSPolyline *testPoly = [GMSPolyline polylineWithPath:trackedPath];
        testPoly.strokeWidth = 8;
        testPoly.strokeColor = [UIColor redColor];
        testPoly.map = myMapView;
    }
}

This doesn't produce any polyline on the map in practice so any help/advice would be much appreciated!

Answer 1

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{  NSString *pointString=[NSString    stringWithFormat:@"%f,%f",newLocation.coordinate.latitude,newLocation.coordinate.longitude];
    [self.points addObject:pointString];
GMSMutablePath *path = [GMSMutablePath path];
for (int i=0; i<self.points.count; i++)
{           
  NSArray *latlongArray = [[self.points   objectAtIndex:i]componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@","]];

[path addLatitude:[[latlongArray objectAtIndex:0] doubleValue] longitude:[[latlongArray objectAtIndex:1] doubleValue]];
 }

if (self.points.count>2)
{
    GMSPolyline *polyline = [GMSPolyline polylineWithPath:path];
    polyline.strokeColor = [UIColor blueColor];
    polyline.strokeWidth = 5.f;
    polyline.map = mapView_;
    self.view = mapView_;
}}