How to decode the Google Directions API polylines field into lat long points in Objective-C for iPhone?

Question

I want to draw routes on a map corresponding to directions JSON which I am getting through the Google Directions API: https://developers.google.com/maps/documentation/direct

Answer 1

For Google maps it already have a straight forward method , polylineWithPath, so I prefer this snippet.

-(void)drawPathFrom:(CLLocation*)source toDestination:(CLLocation*)destination{

    NSString *baseUrl = [NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/directions/json?origin=%f,%f&destination=%f,%f&sensor=true", source.coordinate.latitude,  source.coordinate.longitude, destination.coordinate.latitude,  destination.coordinate.longitude];

    NSURL *url = [NSURL URLWithString:[baseUrl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
    NSLog(@"Url: %@", url);
    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        if(!connectionError){
            NSDictionary *result        = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
            NSArray *routes             = [result objectForKey:@"routes"];
            NSDictionary *firstRoute    = [routes objectAtIndex:0];
            NSString *encodedPath       = [firstRoute[@"overview_polyline"] objectForKey:@"points"];

            GMSPolyline *polyPath       = [GMSPolyline polylineWithPath:[GMSPath pathFromEncodedPath:encodedPath]];
            polyPath.strokeColor        = [UIColor redColor];
            polyPath.strokeWidth        = 3.5f;
            polyPath.map                = _mapView;
        }
    }];

}