How to search MKMapView with UISearchBar ?

Question

I have an application that needs to have a similar search feature like the Apple "Maps" application (included with iPhone/iPod Touch).

The feature in question should not be a hard thing to do, but I'm really clueless about how to input a Street Address in the search bar, and then obtaining coordinates for that address or something that can help me to actually move the map and center in that place.

I mean, what do I have to query, does apple provide an "address searching API method" ? or I need to use the google maps API directly ?

I would love to hear how should be done.

Answer 1

You can use Google's API service to get lat/long coords from a textual search string. Be sure to pass the user's current location so the results are relevant. Read the answers to this question: http://stackoverflow.com/questions/1640932/search-and-display-buisness-locations-on-mkmapview

Answer 2

Ok, to answer my own question:

As was mentioned before, the best thing to do is to use the Google Maps API, this supports a lot of formats but for several reasons I chose to go 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 and this is 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?output=json

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 . )

Answer 3

[self searchCoordinatesForAddress:[searchBar text]];

Hi Mr. Gando, i'm really interested in your solution.

What has searchCoordinatesForAddress inside?

Gracias ;)