Looking up a location using Xcode 5:

by Nicholas Duchon

The idea is to send some information about a location, say a zip code or partial address and get some information about the possible locations - particularly the latitude and longitude of the place(s).

  1. Project should include the CoreLocation framework.
  2.  In the .h file (say viewController.h), add the following:
    1. #import <CoreLocation/CoreLocation.h>
    2. CLGeocoder * geo; // after the interface section, local variable, only need to instantiate this once.
  3. In the .m file, responding to some event, say a button press (but other events are possible):

- (IBAction)fromZip:(id)sender {     // ND: connected to a button on the display
    self.labLat.text = @"234.432";   // ND: some junk default values
    self.latLong.text = @"23.332";
    NSString * st = self.zipCode.text; // ND: get string to search for from a text field in this example
    NSLog(@"%@\n", st);                // ND: print it out just to be sure, debugging

    // ND: create a geo object if it doesn't already exist
    if (geo == NULL) geo = [[CLGeocoder alloc] init];
    // ND: inquiry based on string st - could be partial address, zip code, etc.
    [geo geocodeAddressString:st

    // ND: results of query returned in array - generally just one entry,
    //   so why bother with an array? Who knows, just seems extra messy to me.
                 completionHandler:^(NSArray* placemarks, NSError* error)

     // ND: the following is a block of code that handles the return from the query event
     //     the standard example uses the a for loop just in case there is more than one return
     //     here - handler is the name of a local instance method and placemarks is the name of the
     //     of the array of locations returned from the query.
     {[self handler:placemarks];}
} // end method fromZip - the one that is connected to a button in my example - not shown

// ND: the method called in the block above - at least the block is shorter this way.
- (void) handler:(NSArray *) placemarks{

    // ND: go through all the locations returned, as noted above, this is generally just one place   
    for (CLPlacemark* aPlacemark in placemarks)
        // ND: the following two line put a description of the location on the debug display
        //     this should be removed in your production code
        NSString * st2 = [aPlacemark description];
        NSLog(@"%@\n", st2);
        // ND: this is one way to get the location coordinates in double variables
        // notice that the class relationships are rather complex - try the quick help to see!
        double lat = aPlacemark.location.coordinate.latitude;
        double lon = aPlacemark.location.coordinate.longitude;
        // ND: the following is one way to put some information about the location
        //     returned on the display, labLat, latLong, town and state are names of outlets
        //     on the display I have created as a demo
        self.labLat.text = [[NSString alloc] initWithFormat:@"%f", lat];
        self.latLong.text = [[NSString alloc] initWithFormat:@"%f", lon];
        self.town.text = aPlacemark.locality;
        self.state.text = aPlacemark.administrativeArea;
        // Process the placemark.

} // end handler