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.

Answer 2

Create a singleton class which has a latitude and longitude properties, startLocating and endLocating. In the class, create a CLLocationManager instance, and set its delegate to be the singleton. In startLocating and endLocating, call the appropriate methods of the CLLocationManager instance. Make the delegate methods update the latitude and longitude properties. In other ViewControllers, read this singleton's latitude and longitude properties.

To know when to read those properties from another ViewController, set an observer on these properties (see the NSKeyValueObserving Protocol Reference

Before doing this, look up the Internets for existing code.

After doing this, upload it to GitHub with a permissive license.