Posts Tagged HowTo

iPhone tip #2 – What is my current location?

Posted by Samuel in iPhone on April 9, 2009

The iPhone has GPS built-in, which makes the phone really powerful and enables developers to innovate cool and cutting edge applications!

The iPhone devcenter has some sample code explaining how the CoreLocation framework works. But, I found that example a bit hard to understand…

Here is an easier way of finding your current location from your iPhone.

Let’s start with the interface/header file.
CurrentLocationController.h

#import <CoreLocation/CoreLocation.h>
 
@interface CurrentLocationController : NSObject <CLLocationManagerDelegate> {
	CLLocationManager *locationManager;
}
 
@property (nonatomic, retain) CLLocationManager *locationManager;
 
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation;
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error;
 
@end

Note: Our object “implements” the CLLocationManagerDelegate protocol. We “implement” two methods, locationManager:didUpdateToLocation:fromLocation: and locationManager:didFailWithErrorfrom :, from CLLocationManagerDelegate. The first method is invoked when a new location is available and the second one if an error has occurred.

Here comes the implementation:

#import "CurrentLocationController.h"
 
@implementation CurrentLocationController
 
@synthesize locationManager;
 
- (id) init {
    self = [super init];
    if (self != nil) {
        self.locationManager = [[[CLLocationManager alloc] init] autorelease];
        self.locationManager.delegate = self;
    }
    return self;
}
 
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
    NSLog([newLocation description]);
}
 
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error {
    NSLog([error description]);
}
 
- (void)dealloc {
    [self.locationManager release];
    [super dealloc];
}
 
@end

The only important thing to note is the line

self.locationManager.delegate = self;

. Here we set our own object as the delegate, which means that all the location messages will be forwarded to CurrentLocationController.

I hope this will give you more time innovating, instead of developing Trichotillomania.

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