Autofill city and state from zip code in iOS

Question

I have three textfields in my view. 1. Zip code, 2. City and 3. State.

How to autofill city and state field from the zip code in iOS?

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSString *currentString = [textField.text stringByReplacingCharactersInRange:range withString:string];
    int length = [currentString length];
    if(length > 5)
    {
        return NO;
    }
    if(length == 5)
    {
        [self getCityAndState];
    }
    return YES;
}

- (void) getCityAndState
{
    //How to use google (or any) api to autofill city and state in objective - c?
}

Answer 1

While the answers from alex_c and a-r-studios work well, if you don't feel like fussing with AddressBookUI or dictionaries, you can simply use the geocodeAddressString:completionHandler: method on the geocoder passing in the zip code alone which is sufficient for the lookup:

[[CLGeocoder new] geocodeAddressString:zip completionHandler:^(NSArray *placemarks, NSError *error) {
    if (placemarks.count) {
        CLPlacemark *placemark = placemarks.firstObject;

        NSString *city = placemark.locality;
        NSString *state = placemark.administrativeArea;
    }
}];

In Swift:

CLGeocoder().geocodeAddressString(zip) { (placemarks, error) in
    if let result = placemarks?.first {
        let city = result.locality
        let state = result.administrativeArea
    }
}

Answer 2

I try to avoid Google's services because they tend to charge at a certain level of usage. Here's the solution using Apple's frameworks:

 #import <CoreLocation/CoreLocation.h>
 #import <AddressBookUI/AddressBookUI.h>

- (void)didEnterZip:(NSString*)zip
{
    CLGeocoder* geoCoder = [[CLGeocoder alloc] init];
    [geoCoder geocodeAddressDictionary:@{(NSString*)kABPersonAddressZIPKey : zip} 
      completionHandler:^(NSArray *placemarks, NSError *error) {
        if ([placemarks count] > 0) {
            CLPlacemark* placemark = [placemarks objectAtIndex:0];

            NSString* city = placemark.addressDictionary[(NSString*)kABPersonAddressCityKey];
            NSString* state = placemark.addressDictionary[(NSString*)kABPersonAddressStateKey];
            NSString* country = placemark.addressDictionary[(NSString*)kABPersonAddressCountryCodeKey];

        } else {
            // Lookup Failed
        }
    }];
}