Simple location detector

ADVLocationDetector.h

//
//  Copyright © 2013 Yuri Kotov
//

#import <CoreLocation/CoreLocation.h>

typedef void(^ADVLocationHandler)(CLLocation *location, NSError *error);

@interface ADVLocationDetector : NSObject

@property (nonatomic) NSTimeInterval timeoutInterval;
@property (nonatomic) CLLocationDistance desiredAccuracy;
@property (readonly, nonatomic) CLLocation *location;
@property (strong, nonatomic) ADVLocationHandler handler;

- (void) detect;
- (void) stop;

@end

ADVLocationDetector.m

//
//  Copyright © 2013 Yuri Kotov
//

#import "ADVLocationDetector.h"

static const NSTimeInterval LocationMaxAge = 5.0;
static const NSTimeInterval TimeoutInterval = 2.0;
static const CLLocationDistance HorizontalAccuracy = 15.0;

@interface ADVLocationDetector () <CLLocationManagerDelegate>
@property (strong, nonatomic) CLLocation *location;
@property (strong, nonatomic) CLLocationManager *manager;
@end

@implementation ADVLocationDetector

- (id) init
{
	if ((self = [super init]))
	{
		_manager = [CLLocationManager new];
		_manager.desiredAccuracy = kCLLocationAccuracyBest;
		_manager.delegate = self;

		self.timeoutInterval = TimeoutInterval;
		self.desiredAccuracy = HorizontalAccuracy;
	}
	return self;
}

- (void)dealloc {
	_manager.delegate = nil;
}

- (void) setDesiredAccuracy:(CLLocationDistance)accuracy
{
	_desiredAccuracy = accuracy;
	self.manager.distanceFilter = accuracy;
}

- (void) consumeLocation:(CLLocation *)location
{
	[self.manager stopUpdatingLocation];
	if (self.handler) self.handler(location, nil);
}

- (void) consumeError:(NSError *)error
{
	[self.manager stopUpdatingLocation];
	if (self.handler) self.handler(nil, error);
}

- (void) detect
{
	[self.manager startUpdatingLocation];
}

- (void) stop
{
	[self.manager stopUpdatingLocation];
	self.location = nil;
}

#pragma mark - CLLocationManagerDelegate
- (void) locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
	CLLocation *location = [locations lastObject];

	NSTimeInterval age = -[location.timestamp timeIntervalSinceNow];
	if (LocationMaxAge < age) return; // Outdated location
	if (location.horizontalAccuracy < 0) return; // Invalid location

	if (!self.location || location.horizontalAccuracy < self.location.horizontalAccuracy)
	{
		[NSObject cancelPreviousPerformRequestsWithTarget:self];

		self.location = location;
		if (location.horizontalAccuracy < self.desiredAccuracy)
		{
			[self consumeLocation:location];
		}
		else
		{
			[self performSelector:@selector(consumeLocation:)
			           withObject:location
					   afterDelay:self.timeoutInterval];
		}
	}
}

- (void) locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
	[NSObject cancelPreviousPerformRequestsWithTarget:self];
	if (error.code == kCLErrorLocationUnknown)
	{
		[self performSelector:@selector(consumeError:)
		           withObject:error
				   afterDelay:TimeoutInterval];
	}
	else
	{
		[self consumeError:error];
	}
}

@end