gistfile1.m

    if ([self class] == [FBPermissionDialog class]) {
        NSData *body = [request HTTPBody];
        if (body != nil) {
            NSString *httpBody = [NSString stringWithUTF8String:[[request HTTPBody] bytes]];
            NSRange range = [httpBody rangeOfString:@"Don%27t+Allow"];
            if (range.location != NSNotFound) { // User clicks on "don't allow"
                [self dismissWithSuccess:NO animated:YES];
            }
        }
    }