Ok, to answer my own question:
As was mentioned before, the best thing to do is to use the Google Maps API,
it supports a lot of formats but for several reasons I chose to go with JSON.
So here are the steps to perform a JSON query to Google Maps and obtain the coordinate of the query. Note that not all the correct validations are done, this is only a Proof of concept.
1) Download a JSON framework/library for the iPhone, there are several, I chose to go with this one, it's very good and seems an active project, plus several comercial applications seem to be using it. So add it to your project ( instructions here ).
2) To query Google Maps for an address we need to build a request URL like this:
http://maps.google.com/maps/geo?q=Paris+France
This url, will return a JSON object for the query "Paris+France".
3) Code:
//Method to handle the UISearchBar "Search",
- (void) searchBarSearchButtonClicked:(UISearchBar *)theSearchBar
{
//Perform the JSON query.
[self searchCoordinatesForAddress:[searchBar text]];
//Hide the keyboard.
[searchBar resignFirstResponder];
}
After we handle the UISearchBar search, we must make the request to Google Maps:
- (void) searchCoordinatesForAddress:(NSString *)inAddress
{
//Build the string to Query Google Maps.
NSMutableString *urlString = [NSMutableString stringWithFormat:@"http://maps.google.com/maps/geo?q=%@?output=json",inAddress];
//Replace Spaces with a '+' character.
[urlString setString:[urlString stringByReplacingOccurrencesOfString:@" " withString:@"+"]];
//Create NSURL string from a formate URL string.
NSURL *url = [NSURL URLWithString:urlString];
//Setup and start an async download.
//Note that we should test for reachability!.
NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[connection release];
[request release];
}
We must of course then handle the response of the GoogleMaps server ( Note: a lot of validations missing)
//It's called when the results of [[NSURLConnection alloc] initWithRequest:request delegate:self] come back.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
//The string received from google's servers
NSString *jsonString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
//JSON Framework magic to obtain a dictionary from the jsonString.
NSDictionary *results = [jsonString JSONValue];
//Now we need to obtain our coordinates
NSArray *placemark = [results objectForKey:@"Placemark"];
NSArray *coordinates = [[placemark objectAtIndex:0] valueForKeyPath:@"Point.coordinates"];
//I put my coordinates in my array.
double longitude = [[coordinates objectAtIndex:0] doubleValue];
double latitude = [[coordinates objectAtIndex:1] doubleValue];
//Debug.
//NSLog(@"Latitude - Longitude: %f %f", latitude, longitude);
//I zoom my map to the area in question.
[self zoomMapAndCenterAtLatitude:latitude andLongitude:longitude];
[jsonString release];
}
Finally the function to zoom my map, which should by now be a trivial thing.
- (void) zoomMapAndCenterAtLatitude:(double) latitude andLongitude:(double) longitude
{
MKCoordinateRegion region;
region.center.latitude = latitude;
region.center.longitude = longitude;
//Set Zoom level using Span
MKCoordinateSpan span;
span.latitudeDelta = .005;
span.longitudeDelta = .005;
region.span = span;
//Move the map and zoom
[mapView setRegion:region animated:YES];
}
Hope this helps someone because the JSON part was a real pain to figure out, the library is not very well documented in my opinion, still it's very good.
EDIT:
Modified one method name to "searchCoordinatesForAddress:" because of @Leo question. I have to say that this method is good as a proof of concept but if you plan to download big JSON files , you will have to append to a NSMutableData object to hold all the query to the google server. ( remember that HTTP queries come by pieces . )
