How to make a custom file format

FROM : malcom
DATE : Thu Jul 20 16:11:02 2006

Hello,
I would to add a new file type into my app. It's basically a folder
where I need to read some files. I've tried to add the file format
extensions inside my plist as you can see from this screenshot:

http://img236.imageshack.us/img236/8366/immagine7bb3.png

Unfortunatly If I take a folder and I try to add my fformat suffix the
folder still remain a folder. So I've add a class (ANTFileReader) to
my file format class.
This is the implementation:

@implementation ANTFileReader

+ (NSArray *)readableTypes {
   return [NSArray arrayWithObjects:@"msgnemo",nil];
}

+(NSArray*)writableTypes {
   return [NSArray arrayWithObjects:@"msgnemo",nil];
}

- (BOOL)readFromFileWrapper:(NSFileWrapper *)fileWrapper
ofType:(NSString *)typeName error:(NSError **)outError {
   return YES;
}

@end


It works fine and now the folder is a 'fake-file'. But when I try to
launch my app this is the result:

http://img163.imageshack.us/img163/9533/immagine8ql2.png
http://img163.imageshack.us/img163/6748/immagine9lw9.png

What's wrong?  Need I to implement other methods? Thanks