Question: So I'm trying to register for the MPMoviePlayerDidExitFullscreenNotification notification in my universal app (iPhone and iPad).

Problem is, OS 3.1.3 doesn't support this notification, and just crashes.

I've tried version checking, like so:

```
if ([MPMoviePlayerController instancesRespondToSelector:@selector(setShouldAutoplay:)])
{//Check for shouldSetAutoplay, this ensures that we are running at least 3.2
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playerDidFinish:) name:(NSString*)class2 object:[self player]];

```

Doesn't work, still crashes. How do I do this?

Answer: 
This also works:

```
if (&MPMoviePlayerDidExitFullscreenNotification) {

}

```

Note you have to check the address of the symbol otherwise you will get a crash.
I needed exactly this but I did prefer using `dlsym` as KennyTM suggested, however, I needed to do a small change for it to work so I guess that was a bug (please correct me if I'm wrong). This is the code snippet I'm using which works great:

```
NSString* x_MPMoviePlayerDidExitFullscreenNotification = *(NSString**)dlsym(RTLD_DEFAULT, "MPMoviePlayerDidExitFullscreenNotification");
        if (x_MPMoviePlayerDidExitFullscreenNotification != nil) {
            [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(didExitFullscreen:) name:x_MPMoviePlayerDidExitFullscreenNotification object: self.videoPlayer];
        }

```

The change from KennyTM's snippet was the `*(NSString**)` cast after dlsym as it seems dlsym will return a pointer to the symbol.