xcode - iOS CLLocationManager in a separate class

Question

I have multiple view controllers that need to get the user's location, so I wanted to create a separate class that the ViewControllers can call to get the user's latest location.

locationManager:didUpdateToLocation:fromLocation returns void. How do I pass the latitude and longitude data back to my ViewControllers as soon as the user's latitude and longitude is calculated?

I could try writing getters and setters in my locationManaging class, but if I do that, how do I know when to call the latitude getter and longitude getter methods from my ViewController class? How do I hold the ViewController's main thread to wait for the latitude and longitude values from the locationManaging class?

Thanks!

Answer 1

As user1071136 said, a singleton location manager is probably what you want. Create a class, a subclass of NSObject, with just one property, a CLLocationManager.

LocationManagerSingleton.h:

#import <MapKit/MapKit.h>

@interface LocationManagerSingleton : NSObject <CLLocationManagerDelegate>

@property (nonatomic, strong) CLLocationManager* locationManager;

+ (LocationManagerSingleton*)sharedSingleton;

@end

LocationManagerSingleton.m:

#import "LocationManagerSingleton.h"

@implementation LocationManagerSingleton

@synthesize locationManager;

- (id)init {
    self = [super init];

    if(self) {
        self.locationManager = [CLLocationManager new];
        [self.locationManager setDelegate:self];
        [self.locationManager setDistanceFilter:kCLDistanceFilterNone];
        [self.locationManager setHeadingFilter:kCLHeadingFilterNone];
        [self.locationManager startUpdatingLocation];
        //do any more customization to your location manager
    }

    return self;
}    

+ (LocationManagerSingleton*)sharedSingleton {
    static LocationManagerSingleton* sharedSingleton;
    if(!sharedSingleton) {
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            sharedSingleton = [LocationManagerSingleton new];
        }
    }

    return sharedSingleton;
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    //handle your location updates here
}

- (void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading {
    //handle your heading updates here- I would suggest only handling the nth update, because they
    //come in fast and furious and it takes a lot of processing power to handle all of them
}

@end

To get the most recently received location, simply use [LocationManagerSingleton sharedSingleton].locationManager.location. It might take a few seconds to warm up the GPS to get accurate locations.