Anyway, this time around I am posting a couple of methods that outline how I retrieve a country name by doing a JSON query passing in the latitude and longitude of a place, and secondly how I get the coordinates to a search term (a string).
As usual I'll let the code speak for itself...
To get the string name of a country from latitude and longitude, also with the ability to specify which language you get the country name back in...
// Do reverse geocode lookup on latitude/longitude to get country name based on specified locale
- (NSString*)getCountryNameFromCoordinates:(CLLocationCoordinate2D)coordinates locale:(NSString*)language;
{
NSLog(@"Querying Google location API for %@ country name for latitude %f and longitude %f...", language, coordinates.latitude, coordinates.longitude);
// Get JSON contents from Google API
NSString *url = [[NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/geocode/json?latlng=%f,%f&sensor=false&language=%@", coordinates.latitude, coordinates.longitude, language] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSLog(@"Query URL is: %@", url);
NSError *error = nil;
NSString *jsonString = [NSString stringWithContentsOfURL:[NSURL URLWithString:url] encoding:NSUTF8StringEncoding error:&error];
if (error != nil)
{
NSLog(@"Error doing reverse geocode lookup on %f, %f, lang=%@: %@", coordinates.latitude, coordinates.longitude, language, error.localizedDescription);
return nil;
}
// Extract country by parsing JSON data
SBJsonParser *jsonParser = [[SBJsonParser alloc] init];
error = nil;
NSDictionary *jsonObjects = [jsonParser objectWithString:jsonString error:&error];
if (error != nil)
{
NSLog(@"Error parsing JSON response to reverse geocode lookup: %@", jsonParser.error);
[jsonParser release];
[jsonObjects release];
return nil;
}
NSDictionary *results = [jsonObjects objectForKey:@"results"];
NSString *country = nil;
for (NSDictionary *item in results)
{
if ([[item objectForKey:@"types"] containsObject:@"country"])
{
country = [[[item objectForKey:@"address_components"] objectAtIndex:0] objectForKey:@"long_name"];
NSLog(@"Found matching country name: %@", country);
[item release];
break;
}
[item release];
}
if (country == nil) {
NSLog(@"Couldn't find a matching country name");
[jsonParser release];
[jsonObjects release];
[results release];
[country release];
return nil;
}
[jsonParser release];
[jsonObjects release];
[results release];
return country;
}
And to center your map (or whatever behaviour you so desire) on the coordinates obtained from a search on a specified location string...
- (void)searchCoordinatesForAddress:(NSString *)inAddress
{
NSLog(@"Querying Google location API for latitude/longitude coordinates for search term %@", inAddress);
// Get JSON contents from Google API
NSString *url = [[NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/geocode/json?address=%@&sensor=false", inAddress] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSLog(@"Query URL is: %@", url);
NSError *error = nil;
NSString *jsonString = [NSString stringWithContentsOfURL:[NSURL URLWithString:url] encoding:NSUTF8StringEncoding error:&error];
if (error != nil)
{
NSLog(@"Error doing coordinate lookup on %@: %@", inAddress, error.localizedDescription);
return;
}
// Extract coordinates by parsing JSON data
SBJsonParser *jsonParser = [[SBJsonParser alloc] init];
error = nil;
NSDictionary *jsonObjects = [jsonParser objectWithString:jsonString error:&error];
if (error != nil)
{
NSLog(@"Error parsing JSON response to extract coordinates: %@", jsonParser.error);
[jsonParser release];
[jsonObjects release];
return;
}
NSArray *results;
NSDictionary *location;
@try {
results = [jsonObjects objectForKey:@"results"];
location = [[[results objectAtIndex:0] objectForKey:@"geometry"] objectForKey:@"location"];
}
@catch (NSException *exception) {
NSLog(@"Could not find searched location's coordinates");
[jsonParser release];
[jsonObjects release];
return;
}
// Get latitude and longitude as double values
double longitude = 0.0;
double latitude = 0.0;
NSNumber *lat = [location objectForKey:@"lat"];
NSNumber *lng = [location objectForKey:@"lng"];
latitude = [lat doubleValue];
longitude = [lng doubleValue];
[lat release];
[lng release];
[jsonParser release];
[jsonObjects release];
[results release];
if (longitude == 0 && latitude == 0) {
NSLog(@"Could not find searched location's coordinates");
return;
}
NSLog(@"Coordinates found for searched location: %f %f", latitude, longitude);
// I zoom my map to the area in question.
[self zoomMapAndCenterAtLatitude:latitude andLongitude:longitude];
}
