What's the easiest way to get the current location of an iPhone?

Question

I already know how to use the CLLocationManager, so I could do it the hard way, with delegates and all that.

But I'd like to have a convenience method that just gets the current location, once, and blocks until it gets the result.

Answer 1

What I do is implement a singleton class to manage updates from core location. To access my current location, I do a CLLocation *myLocation = [[LocationManager sharedInstance] currentLocation]; If you wanted to block the main thread you could do something like this:

while ([[LocationManager sharedInstance] locationKnown] == NO){    //blocking here    //do stuff here, dont forget to have some kind of timeout to get out of this blocked    //state } 

However, as it has been already pointed out, blocking the main thread is probably not a good idea, but this can be a good jumping off point as you are building something. You will also notice that the class I wrote checks the timestamp on location updates and ignores any that are old, to prevent the problem of getting stale data from core location.

This is the singleton class I wrote. Please note that it is a little rough around the edges:

#import <CoreLocation/CoreLocation.h> #import <Foundation/Foundation.h>  @interface  LocationController : NSObject <CLLocationManagerDelegate> {     CLLocationManager *locationManager;     CLLocation *currentLocation; }  + (LocationController *)sharedInstance;  -(void) start; -(void) stop; -(BOOL) locationKnown;  @property (nonatomic, retain) CLLocation *currentLocation;  @end @implementation LocationController  @synthesize currentLocation;  static LocationController *sharedInstance;  + (LocationController *)sharedInstance {     @synchronized(self) {         if (!sharedInstance)             sharedInstance=[[LocationController alloc] init];            }     return sharedInstance; }  +(id)alloc {     @synchronized(self) {         NSAssert(sharedInstance == nil, @"Attempted to allocate a second instance of a singleton LocationController.");         sharedInstance = [super alloc];     }     return sharedInstance; }  -(id) init {     if (self = [super init]) {         self.currentLocation = [[CLLocation alloc] init];         locationManager = [[CLLocationManager alloc] init];         locationManager.delegate = self;         [self start];     }     return self; }  -(void) start {     [locationManager startUpdatingLocation]; }  -(void) stop {     [locationManager stopUpdatingLocation]; }  -(BOOL) locationKnown {       if (round(currentLocation.speed) == -1) return NO; else return YES;  }  - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {     //if the time interval returned from core location is more than two minutes we ignore it because it might be from an old session     if ( abs([newLocation.timestamp timeIntervalSinceDate: [NSDate date]]) < 120) {              self.currentLocation = newLocation;     } }  - (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {     UIAlertView *alert;     alert = [[UIAlertView alloc] initWithTitle:@"Error" message:[error description] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];     [alert show];     [alert release]; }  -(void) dealloc {     [locationManager release];     [currentLocation release];     [super dealloc]; }  @end 

Answer 2

There is no such convenience and you shouldn't create your own. "Blocks until it gets the result" is extremely bad programming practice on a device like the iPhone. It can take seconds to retrieve a location; you should never make your users wait like that, and delegates ensure they don't.