IPhone : Using MapKit types in Swift Programming

I am having a hard time getting the type of the map to switch types.

    @IBAction func changeMapType(sender: AnyObject) {
    if mapView.mapType == MKMapType.Standard {
        mapView.mapType == MKMapType.Satellite
    }
    else {
        mapView.mapType == MKMapType.Standard
    }
}

I was following this guide http://www.techotopia.com/index.php/Working_with_Maps_on_iOS_8_with_Swift%2C_MapKit_and_the_MKMapView_Class and made it to the end, and it will zoom but it will not change types. They used the code:

- (IBAction)changeMapType:(id)sender {
if mapView.mapType == MKMapType.Standard {
    mapView.mapType = MKMapType.Satellite
} else {
    mapView.mapType = MKMapType.Standard
}

}

but i really don't understand why.