Polyline for MKMapView not working - objective-c

Question

I've been trying and trying to get this poly line to work in Objective C. I've been through every tutorial I can find and gotten nowhere, I cant see whats wrong with it.
CLLocationCoordinate2D coordinateArray2[2];
coordinateArray2[1].longitude = 176.8773669;
coordinateArray2[0].longitude = 176.88151896;
coordinateArray2[0].latitude = -39.668593;
coordinateArray2[1].latitude = -39.67018069;
_route1Line = [MKPolyline polylineWithCoordinates:coordinateArray2 count:2];
[_GPSView setDelegate:self];
[_GPSView addOverlay:_route1Line];
_testlabel.text = [NSString stringWithFormat:#"%f", coordinateArray2[0].longitude];
can anyone see what is wrong?
header:
#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>
extern int routenumber; //holds current route ID
extern BOOL inRoute; //holds if on route or not
extern int followYou; //holds if the app should follow the user or predefined coordinates
extern NSArray *routeHolder; //holds array of routes
#interface ViewController : UIViewController <MKMapViewDelegate>
#property (weak, nonatomic) IBOutlet MKMapView *GPSView; //adding the map view to the controller
#property (nonatomic, retain) MKPolyline *route1Line; //line for this route
#property (weak, nonatomic) IBOutlet UILabel *testlabel;
#end

Answer 1

You should implement the following method of MKMapViewDelegate:
- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay
{
MKOverlayPathRenderer *theOverlayPathRenderer;
{
theOverlayPathRenderer = [[MKPolylineRenderer alloc] initWithPolyline:overlay];
theOverlayPathRenderer.lineWidth = ...;
theOverlayPathRenderer.fillColor = ...;
theOverlayPathRenderer.strokeColor = ...;
}
return theOverlayPathRenderer;
}

Answer 2

I'm not at a Mac at the moment so I can't run your code, but it looks like you've created your MKPolyline alright, but you're missing the MKPolylineView.
_polylineView = [MKPolylineView alloc] initWithPolyline:route1Line]; // Declare it in your header file or in the implementation's interface.
_polylineView.strokeColor = [UIColor redColor];
_polylineView.lineWidth = 5.0
Then make sure you conform to the MKMapViewDelegate and implement mapView:viewForOverlay
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay {
return _polylineView;
}