Change starting location when opening Apple Maps from within app - objective-c

Question

By default when opening Apple Maps through a MKMapItem it uses the device's location as the starting point but i'm trying to allow a user to add their own starting point by entering in the proper fields (address, city, state, zipcode) and passing the address string to
CLGeocoder *geocoder = [[CLGeocoder alloc] init];
NSString *addressString = [NSString stringWithFormat:#"%# %# %# %#",
self.address.text,
self.city.text,
self.state.text,
self.zip.text];
[geocoder geocodeAddressString:addressString
completionHandler:^(NSArray *placemarks, NSError *error)
{
CLLocationCoordinate2D addressCoordinates;
if (error.code == 2)
{
UIAlertView *networkConnectionAlert = [[UIAlertView alloc] initWithTitle:#"Network Error" message:#"The internet connections appears to be offline. Ensure that data is enabled or that your device is connected to a wireless connection." delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[networkConnectionAlert show];
NSLog(#"Geocode failed with error: %#", error);
return;
}
if (placemarks && placemarks.count > 0)
{
CLPlacemark *placemark = placemarks[0];
// Location of address passed in
CLLocation *location = placemark.location;
// Coordinates of address passed in
addressCoordinates = location.coordinate;
}
// Destination address dictionary values
NSDictionary *address = #{
(NSString *)kABPersonAddressStreetKey: self.address.text,
(NSString *)kABPersonAddressCityKey: self.city.text,
(NSString *)kABPersonAddressStateKey: self.state.text,
(NSString *)kABPersonAddressZIPKey: self.zip.text
};
MKPlacemark *place = [[MKPlacemark alloc] initWithCoordinate:addressCoordinates
addressDictionary:address];
MKMapItem *mapItem = [[MKMapItem alloc]initWithPlacemark:place];
NSDictionary *options = #{MKLaunchOptionsDirectionsModeKey:MKLaunchOptionsDirectionsModeDriving};
[mapItem openInMapsWithLaunchOptions:options];
}];
Of course every time I run the app it uses the device's location as the starting point and the destination point as the address entered which is understandable given the code above but is there not a property that can be called to change the starting point? I know that you can change the starting address/location when you open the actual Apple Maps so I assume that there has to be a way and that I'm just doing something wrong or missing something. Any help on this would be greatly appreciated, thanks.