xmppframework use

Get the server delay the date, the following code:

XMPPElement * xmppElement = [[XMPPElement alloc] init];
if ([xmppElement wasDelayed] {
delayDate = [xmppElement delayedDeliveryDate];
}


But Tip - [DDXMLInvalidNode wasDelayed]: unrecognized selector sent to instance 0x6e3a720
Reply:
Library reference error
Reply:
Such errors are not looking under way to find.