What I usually do in this type of situation is pass nil
as the argument:
[self orientationChanged:nil];
This depends on how critical the notification itself is to the implementation of the method. You may have to construct a notification with the appropriate information in it:
NSNotification *n = [NSNotification notificationWithName:@"someName" object:someObject];
[self orientationChanged:n];
However, I have come to view this type of need as a code smell, what I try to do instead is extract the work the notification handler performs into a separate method and call that one directly, e.g.:
- (void)handleOrientationChangeForDevice:(UIDevice *)d {
// do something here
}
- (void)orientationChanged:(NSNotification *)n {
[self handleOrientationChangeForDevice:n.object];
}
Then, in the calling code, you could do something like:
[self handleOrientationChangeForDevice:[UIDevice currentDevice]];