How to set different role of node in INET like MiXiM

Question

Omnet++ 5.0 and INET 3.4

I want to simulate a MAC protocol base BMAC, however, nodes in the net topology have different function. So I set a enum called role in .h file and add several handlemsg function in .cc file
like below codes in the MiXiM

    //in .cc file add 
     enum ROLES {
        NODE_RECEIVER,      // 0
        NODE_SENDER,        // 1
    };
    ROLES role;

   //in .h flie add
   void XXXMacLayer::handleSelfMsg(cMessage *msg) {
   // Check role of this node
        if (role == NODE_SENDER) {
           handleSelfMsgSender(msg);
        } 
        else {
           handleSelfMsgReceiver(msg);
        }
    }

however, there is a warning "Member 'role' was not initialized in this constructor"
Anyone can give me some advice or some examples to solve this problem? Thanks in advance!