How to fit bounds for coordinate array with google maps sdk for iOS?

Swift 5 version of Lirik's answer:

    func focusMapToShowAllMarkers() {

        if arrMarkers.count > 0 {
            let firstLocation = (arrMarkers.first!).position
            var bounds = GMSCoordinateBounds(coordinate: firstLocation, coordinate: firstLocation)

            for marker in arrMarkers {
              bounds = bounds.includingCoordinate(marker.position)
            }

           let update = GMSCameraUpdate.fit(bounds, withPadding: CGFloat(15))
           self.mapView.animate(with: update)
        }
    }

For time being, Google has finally implemented the GMSCoordinateBounds, you can make use of it with GMSCameraUpdate.

For details, please check the official reference.

Here's my solution for this problem. Building a GMSCoordinateBounds object by multiple coordinates.

- (void)focusMapToShowAllMarkers {       
    CLLocationCoordinate2D myLocation = ((GMSMarker *)_markers.firstObject).position;
    GMSCoordinateBounds *bounds = [[GMSCoordinateBounds alloc] initWithCoordinate:myLocation coordinate:myLocation];

    for (GMSMarker *marker in _markers)
        bounds = [bounds includingCoordinate:marker.position];

    [_mapView animateWithCameraUpdate:[GMSCameraUpdate fitBounds:bounds withPadding:15.0f]];
}

Updated answer: Since GMSMapView markers property is deprecated, you should save all markers in your own array.

updated swift 3 answer:

    func focusMapToShowAllMarkers() {
        let firstLocation = (markers.first as GMSMarker).position
        var bounds = GMSCoordinateBoundsWithCoordinate(firstLocation, coordinate: firstLocation)
    
        for marker in markers {
            bounds = bounds.includingCoordinate(marker.position)
        }
        let update = GMSCameraUpdate.fitBounds(bounds, withPadding: CGFloat(15))
        self.mapView.animate(cameraUpdate: update)
  }

Swift 3.0 version of Lirik's answer:

func focusMapToShowAllMarkers() {
    let myLocation: CLLocationCoordinate2D = self.markers.first!.position
    var bounds: GMSCoordinateBounds = GMSCoordinateBounds(coordinate: myLocation, coordinate: myLocation)

    for marker in self.markers {
        bounds = bounds.includingCoordinate(marker.position)
        self.mapView.animate(with: GMSCameraUpdate.fit(bounds, withPadding: 15.0))
    }
}

And here's my own way:

func focusMapToShowMarkers(markers: [GMSMarker]) {

    guard let currentUserLocation = self.locationManager.location?.coordinate else {
        return
    }

    var bounds: GMSCoordinateBounds = GMSCoordinateBounds(coordinate: currentUserLocation,
                                                          coordinate: currentUserLocation)

    _ = markers.map {
        bounds = bounds.includingCoordinate($0.position)
        self.mapView.animate(with: GMSCameraUpdate.fit(bounds, withPadding: 15.0))
    }
}

And you can call my function above like so:

self.focusMapToShowMarkers(markers: [self.myLocationMarker, currentPokemonMarker])