myclcontroller.m

This is an example application that shows how to use the Location services on the iPhone.

/*

File: MyCLController.m
Abstract: Singleton class used to talk to CoreLocation and send results back to
the app's view controllers.

Version: 1.1

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*/

#import "MyCLController.h"

// Shorthand for getting localized strings, used in formats below for readability
#define LocStr(key) [[NSBundle mainBundle] localizedStringForKey:(key) value:@"" table:nil]


// This is a singleton class, see below
static MyCLController *sharedCLDelegate = nil;

@implementation MyCLController

@synthesize delegate, locationManager;

- (id) init {
	self = [super init];
	if (self != nil) {
		self.locationManager = [[[CLLocationManager alloc] init] autorelease];
		self.locationManager.delegate = self; // Tells the location manager to send updates to this object
	}
	return self;
}


// Called when the location is updated
- (void)locationManager:(CLLocationManager *)manager
	didUpdateToLocation:(CLLocation *)newLocation
		   fromLocation:(CLLocation *)oldLocation
{
	NSMutableString *update = [[[NSMutableString alloc] init] autorelease];
	
	// Timestamp
	NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init]  autorelease];
	[dateFormatter setDateStyle:NSDateFormatterMediumStyle];
	[dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
	[update appendFormat:@"%@\n\n", [dateFormatter stringFromDate:newLocation.timestamp]];
	
	// Horizontal coordinates
	if (signbit(newLocation.horizontalAccuracy)) {
		// Negative accuracy means an invalid or unavailable measurement
		[update appendString:LocStr(@"LatLongUnavailable")];
	} else {
		// CoreLocation returns positive for North & East, negative for South & West
		[update appendFormat:LocStr(@"LatLongFormat"), // This format takes 4 args: 2 pairs of the form coordinate + compass direction
			fabs(newLocation.coordinate.latitude), signbit(newLocation.coordinate.latitude) ? LocStr(@"South") : LocStr(@"North"),
			fabs(newLocation.coordinate.longitude),	signbit(newLocation.coordinate.longitude) ? LocStr(@"West") : LocStr(@"East")];
		[update appendString:@"\n"];
		[update appendFormat:LocStr(@"MeterAccuracyFormat"), newLocation.horizontalAccuracy];
	}
	[update appendString:@"\n\n"];

	// Altitude
	if (signbit(newLocation.verticalAccuracy)) {
		// Negative accuracy means an invalid or unavailable measurement
		[update appendString:LocStr(@"AltUnavailable")];
	} else {
		// Positive and negative in altitude denote above & below sea level, respectively
		[update appendFormat:LocStr(@"AltitudeFormat"), fabs(newLocation.altitude),	(signbit(newLocation.altitude)) ? LocStr(@"BelowSeaLevel") : LocStr(@"AboveSeaLevel")];
		[update appendString:@"\n"];
		[update appendFormat:LocStr(@"MeterAccuracyFormat"), newLocation.verticalAccuracy];
	}
	[update appendString:@"\n\n"];
	
	// Calculate disatance moved and time elapsed, but only if we have an "old" location
	//
	// NOTE: Timestamps are based on when queries start, not when they return. CoreLocation will query your
	// location based on several methods. Sometimes, queries can come back in a different order from which
	// they were placed, which means the timestamp on the "old" location can sometimes be newer than on the
	// "new" location. For the example, we will clamp the timeElapsed to zero to avoid showing negative times
	// in the UI.
	//
	if (oldLocation != nil) {
		CLLocationDistance distanceMoved = [newLocation getDistanceFrom:oldLocation];
		NSTimeInterval timeElapsed = [newLocation.timestamp timeIntervalSinceDate:oldLocation.timestamp];
		
		[update appendFormat:LocStr(@"LocationChangedFormat"), distanceMoved];
		if (signbit(timeElapsed)) {
			[update appendString:LocStr(@"FromPreviousMeasurement")];
		} else {
			[update appendFormat:LocStr(@"TimeElapsedFormat"), timeElapsed];
		}
		[update appendString:@"\n\n"];
	}
	
	// Send the update to our delegate
	[self.delegate newLocationUpdate:update];
}


// Called when there is an error getting the location
- (void)locationManager:(CLLocationManager *)manager
	   didFailWithError:(NSError *)error
{
	NSMutableString *errorString = [[[NSMutableString alloc] init] autorelease];

	if ([error domain] == kCLErrorDomain) {

		// We handle CoreLocation-related errors here

		switch ([error code]) {
			// This error code is usually returned whenever user taps "Don't Allow" in response to
			// being told your app wants to access the current location. Once this happens, you cannot
			// attempt to get the location again until the app has quit and relaunched.
			//
			// "Don't Allow" on two successive app launches is the same as saying "never allow". The user
			// can reset this for all apps by going to Settings > General > Reset > Reset Location Warnings.
			//
			case kCLErrorDenied:
				[errorString appendFormat:@"%@\n", NSLocalizedString(@"LocationDenied", nil)];
				break;

			// This error code is usually returned whenever the device has no data or WiFi connectivity,
			// or when the location cannot be determined for some other reason.
			//
			// CoreLocation will keep trying, so you can keep waiting, or prompt the user.
			//
			case kCLErrorLocationUnknown:
				[errorString appendFormat:@"%@\n", NSLocalizedString(@"LocationUnknown", nil)];
				break;

			// We shouldn't ever get an unknown error code, but just in case...
			//
			default:
				[errorString appendFormat:@"%@ %d\n", NSLocalizedString(@"GenericLocationError", nil), [error code]];
				break;
		}
	} else {
		// We handle all non-CoreLocation errors here
		// (we depend on localizedDescription for localization)
		[errorString appendFormat:@"Error domain: \"%@\"  Error code: %d\n", [error domain], [error code]];
		[errorString appendFormat:@"Description: \"%@\"\n", [error localizedDescription]];
	}

	// Send the update to our delegate
	[self.delegate newLocationUpdate:errorString];
}

#pragma mark ---- singleton object methods ----

// See "Creating a Singleton Instance" in the Cocoa Fundamentals Guide for more info

+ (MyCLController *)sharedInstance {
    @synchronized(self) {
        if (sharedCLDelegate == nil) {
            [[self alloc] init]; // assignment not done here
        }
    }
    return sharedCLDelegate;
}

+ (id)allocWithZone:(NSZone *)zone {
    @synchronized(self) {
        if (sharedCLDelegate == nil) {
            sharedCLDelegate = [super allocWithZone:zone];
            return sharedCLDelegate;  // assignment and return on first allocation
        }
    }
    return nil; // on subsequent allocation attempts return nil
}

- (id)copyWithZone:(NSZone *)zone
{
    return self;
}

- (id)retain {
    return self;
}

- (unsigned)retainCount {
    return UINT_MAX;  // denotes an object that cannot be released
}

- (void)release {
    //do nothing
}

- (id)autorelease {
    return self;
}

@end