Small library to do reverse geocoding (translating a lat/lon pair into an address)

ReverseGeocoder.h

//  Created by Marcel Molina Jr on 10/8/08.
//

#import <UIKit/UIKit.h>
#import <JSON/JSON.h>
#import <CoreLocation/CoreLocation.h>
@class ReverseGeocoder;
@protocol ReverseGeocoderDelegate
- (void)reverseGeocoder:(ReverseGeocoder *)geocoder
                  lookupReturnedAddress:(NSString *)address;
@end


@interface ReverseGeocoder : NSObject {
    NSURL *_url;
    NSString *_responseBody;
    CLLocationDegrees latitude;
    CLLocationDegrees longitude;
    NSMutableString *responsePayload;
    NSDictionary *addressDictionary;
    NSObject<ReverseGeocoderDelegate> *delegate;
}
@property (nonatomic, retain) NSString *responsePayload;
@property (nonatomic, retain) NSDictionary *addressDictionary;
@property (nonatomic, retain) NSObject<ReverseGeocoderDelegate> *delegate;
+ (void)lookupLatitude:(CLLocationDegrees)aLatitude longitude:(CLLocationDegrees)aLongitude delegate:(id)aDelegate;
- (id)initWithLatitude:(CLLocationDegrees)aLatitude longitude:(CLLocationDegrees)aLongitude;
- (void)performLookup;
- (NSURL *)url;
- (void)parsePayload;

- (NSString *)address;
- (NSString *)streetNumber;
- (NSString *)street;
- (NSString *)city;
- (NSString *)state;
- (NSString *)_valueForAddressComponentNamed:(NSString *)componentName;
@end

ReverseGeocoder.m

//  Created by Marcel Molina Jr on 10/8/08.
//

#import "ReverseGeocoder.h"
#define CoordinateTranslationDomain @"http://ws.geonames.org"
#define CoordinateTranslationPath @"findNearestAddressJSON"

@implementation ReverseGeocoder
@synthesize responsePayload, addressDictionary, delegate;

+ (void)lookupLatitude:(CLLocationDegrees)aLatitude 
             longitude:(CLLocationDegrees)aLongitude 
              delegate:(id)aDelegate
{
    ReverseGeocoder *reverseGeocoder;
    reverseGeocoder = [[[ReverseGeocoder alloc] 
                        initWithLatitude:aLatitude
                                longitude:aLongitude] autorelease];
    reverseGeocoder.delegate = aDelegate;
    [reverseGeocoder performLookup];
}

- (id)initWithLatitude:(CLLocationDegrees)aLatitude 
             longitude:(CLLocationDegrees)aLongitude
{
    self = [super init];
    if (self != nil) {
        latitude = aLatitude;
        longitude = aLongitude;
        self.responsePayload = [[NSMutableString alloc] init];
    }
    return self;
}


- (void)performLookup
{
    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:[self url]];
    NSLog(@"Reverse geolocation url: %@", [self url]);
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [connection release];
    [request release];
}

- (NSURL *)url
{
    if (_url == nil) {
        _url = [NSURL URLWithString:[NSString stringWithFormat:@"%@/%@?lat=%f&lng=%f", 
                                     CoordinateTranslationDomain, CoordinateTranslationPath, 
                                     latitude, longitude]
                ];
    }
    return _url;
}

- (void)parsePayload
{
    SBJSON *json = [[SBJSON new] autorelease];
    NSError *error;
    NSDictionary *parsedJSON;
    parsedJSON = [json objectWithString:responsePayload error:&error];
    self.addressDictionary = [parsedJSON valueForKey:@"address"];
}

- (NSString *)address
{
    return [NSString stringWithFormat:@"%@ %@, %@, %@",
                        [self streetNumber],
                        [self street],
                        [self city],
                        [self state]];
}

- (NSString *)streetNumber
{
    return [self _valueForAddressComponentNamed:@"streetNumber"];
}
    
- (NSString *)street
{
    return [self _valueForAddressComponentNamed:@"street"];
}
    
- (NSString *)city
{
    return [self _valueForAddressComponentNamed:@"placename"];
}
    
- (NSString *)state
{
    return [self _valueForAddressComponentNamed:@"adminCode1"];
}
    
- (NSString *)_valueForAddressComponentNamed:(NSString *)componentName
{
    return [addressDictionary valueForKey:componentName];
}

- (void)dealloc 
{
    [responsePayload release];
    [addressDictionary release];
    [_url release];
    [_responseBody release];
    [delegate release];
    [super dealloc];
}

- (void)notifyDelegate
{
    [delegate reverseGeocoder:self lookupReturnedAddress:[self address]];
}

#pragma mark NSURLConnection delegate methods
- (void)connection:(NSURLConnection *)connection
    didReceiveData:(NSData *)data {
	NSString *newText = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
	if (newText != NULL) {
		[responsePayload appendString:newText];
		[newText release];
	}
}

- (void)connectionDidFinishLoading:(NSURLConnection*)connection {
    NSLog(@"Response payload: %@", responsePayload);
    [self parsePayload];
    NSLog(@"Address: %@", [self address]);
    [self notifyDelegate];
}
@end