Swift
let mapView = MKMapView(frame: CGRect(x: 0, y: 0, width: 320, height: 500))
It's recommended to store the mapView as a property of the containing ViewController
since you might want to access it in more complex implementations.
Objective C
self.map = [[MKMapView alloc]initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
[self.view addSubview:self.map];