How to launch Google Maps on iPhone via web link?

may help you . This is the code I use in one of my apps and it works fine with 3.1. The parameters for Google maps are documented here.

CLLocationCoordinate2D stationLocation = ...

NSString *urlString = [[NSString alloc]
     initWithFormat:@"http://maps.google.com/maps?saddr=%f,%f&daddr=%f,%f&dirflg=d",
        curLocation.latitude,
        curLocation.longitude,
        stationLocation.latitude,
        stationLocation.longitude];

NSURL *aURL = [NSURL URLWithString:urlString];
[urlString release];
[[UIApplication sharedApplication] openURL:aURL]; 

hop of those help? I have read a lot of topics, but i don't find when i want , Try this

    UIApplication *app = [UIApplication sharedApplication];

    NSURL *url = [[NSURL alloc] initWithString: @"http://maps.google.com/maps?saddr=41.029598,28.972985&daddr=41.033586,28.984546"];

    [app openURL:url];

    [url release];

seems to work fine I've just tried your second approach (with addingPercentEncoding(withAllowedCharacters:) and provided the given coordinate and got exactly the same error in Google Maps app.
But then I changed coordinate to the one that is in my city and voila! it worked. Seems like google maps simply couldn't generate directions given the (-20.021999, 57.579075) pair. And judging by your second screenshot (with web version presented – it is blank, no map is presented) I think it's struggling with generating directions in your case too. Why does it tell that the link is not supported in such case puzzles me though.

import UIKit


class ViewController: UIViewController {
  override func loadView() {
    super.loadView()
    let lat = 51.150992
    let long = 71.426444
    let string = "https://www.google.com/maps/dir/?api=1&destination=\(lat),\(long)"
    let encoded = string.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)!
    let url = URL(string: encoded)!
    UIApplication.shared.open(url)
  }
}