Trouble while getting distance between two points - ios

Question

In my iOS app I've to track the distance from a a start point to my current location. I implemented this code:
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
CLLocation *currentLocation = [locations lastObject];
CLLocation *startLocation = [locations firstObject];
[coordArray addObject:currentLocation];
float speed = currentLocation.speed * 3.6;
if (speed > 0) {
self.labelSpeed.text = [NSString stringWithFormat:#"%.2f Km/h", speed];
[speedArray addObject:[NSNumber numberWithFloat:speed]];
}
CLLocationDistance distance = [startLocation distanceFromLocation:currentLocation];
}
But when I try to use the app it doesn't get a distance. I need the distance to show it in a label and with distance I will calculate the number of steps by using this equation:
steps = distance / length of human step
I know that it's not accurate, but I can't use accelerometer, because it doesn't work while the display of the iPhone is not active. A person suggested me this solution. Why my code doesn't give me a distance?

Answer 1

The callback
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
does give you at least one location, and locations array hold sonly multiple objects if the location update was deferred before. To get the walking/driving distance, you have to store the initial location in a class variable or property. Then, when you want to calculate a distance, do as in your code above, but with the class variable that holds the initial location.

Answer 2

Check below code for getting distance:
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations {
if ([coordArray count]>0) {
CLLocation *currentLocation = manager.location;
CLLocation *startLocation = [coordArray objectAtIndex:0];
[coordArray addObject:currentLocation];
float speed = currentLocation.speed * 3.6;
if (speed > 0) {
NSLog(#"\n speed:%#",[NSString stringWithFormat:#"%.2f Km/h", speed]);
}
CLLocationDistance distance = [startLocation distanceFromLocation:currentLocation];
if (distance>0) {
NSLog(#"Distance:%#",[NSString stringWithFormat:#"%lf meters",distance]);
}
}
else{
[coordArray addObject:manager.location];
}
}