Example on how to determine Facebook app invite completion state

fbAppInviteDelegateExample.m

#pragma mark - Facebook App Invite Delegate

- (void)appInviteDialog:(FBSDKAppInviteDialog *)appInviteDialog didCompleteWithResults:(NSDictionary *)results
{
    NSLog(@"app invite result: %@", results);
    
    BOOL complete = [[results valueForKeyPath:@"didComplete"] boolValue];
    NSString *completionGesture = [results valueForKeyPath:@"completionGesture"];
    
    // NOTE: the `cancel` result dictionary will be
    // {
    //   completionGesture = cancel;
    //   didComplete = 1;
    // }
    // else, it will only just `didComplete`
    
    if (completionGesture && [completionGesture isEqualToString:@"cancel"]) {
        // handle cancel state...
        return;
    }
    
    if (complete) { // if completionGesture is nil -> success
        [SVProgressHUD showSuccessWithStatus:NSLocalizedString(@"Your invite has been sent.", nil)];
    }
}

- (void)appInviteDialog:(FBSDKAppInviteDialog *)appInviteDialog didFailWithError:(NSError *)error
{
    NSLog(@"app invite error: %@", error.localizedDescription);
    // handle error...
}