Create and initialize the GMSMapView programmatically.

ViewController.m

@interface ViewController ()

@property (nonatomic) GMSMapView *mapView;

@end

@implementation ViewController

#pragma mark - UIViewController
- (void)viewDidLoad {
    
    [super viewDidLoad];
	
    GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:41.0109 longitude:28.998 zoom:6];
    CGRect mapSize = CGRectMake(self.view.bounds.origin.x, self.view.bounds.origin.y,
                                 self.view.bounds.size.width/2.0,
                                 self.view.bounds.size.height/2.0);
    self.mapView = [GMSMapView mapWithFrame:mapSize camera:camera];
    [self.view addSubview:self.mapView];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end