Question

I am writing a program to control a auto home brewing system on an Arduino Mega micro controller (written in C/C++). In short, what the program is doing is there is a C# application which periodically sends messages through USB to the micro controller. There is then a messaging interface which I wrote which reads the message, and forwards it to whichever component the message is for. Each message is 16 bytes long, the first 4 is a transaction code, and the last 12 is for data. Now, I read in the message and forward to it to my StateController class. It comes in from the InboundMessage function. What I am trying to do is I have a struct (defined in StateController.h) which contains the transaction code and pointer to a member function within StateController. I defined a QueueList (just a simple linked list library), and pushed a bunch of these structs into it. What I would like to do is then when a message comes into the inboundMessage function, i would like to loop through the linked list until I find a transaction code which matches, and then call the member function which is for that message, passing it the data in the message.

I think I have everything initialized correctly, but here is the problem. When I try and compile I get an error saying “func does not exist in this scope”. I have looked all over for a solution to this, but can not find one. My codes is below

StateController.cpp

StateController::StateController(){
  currentState = Idle;
  prevState = Idle;
  lastRunState = Idle;

  txnTable.push((txnRow){MSG_BURN, &StateController::BURNprocessor});
  txnTable.push((txnRow){MSG_MANE, &StateController::MANEprocessor});
  txnTable.push((txnRow){MSG_MAND, &StateController::MANDprocessor});
  txnTable.push((txnRow){MSG_PUMP, &StateController::PUMPprocessor});
  txnTable.push((txnRow){MSG_STAT, &StateController::STATprocessor});  
  txnTable.push((txnRow){MSG_SYNC, &StateController::SYNCprocessor});
  txnTable.push((txnRow){MSG_VALV, &StateController::VALVprocessor});
}

void StateController::inboundMessage(GenericMessage msg){
  // Read transaction code and do what needs to be done for it

  for (int x = 0; x < txnTable.count(); x++)
  {
    if (compareCharArr(msg.code, txnTable[x].code, TXN_CODE_LEN) == true)
    {
      (txnTable[x].*func)(msg.data);
      break;
    }
  }
}

StateController.h

class StateController{
  // Public functions
  public:

    // Constructor
    StateController();

    // State Controller message handeler
    void inboundMessage(GenericMessage msg);

    // Main state machine
    void doWork();

  // Private Members
  private:  

    // Hardware interface
    HardwareInterface hardwareIntf;

    // Current state holder
    StateControllerStates currentState;

    // Preveous State
    StateControllerStates prevState;

    // Last run state
    StateControllerStates lastRunState;

    // BURN Message Processor
    void BURNprocessor(char data[]);

    // MANE Message Processor
    void MANEprocessor(char data[]);

    // MAND Message Processor
    void MANDprocessor(char data[]);

    // PUMP Message Processor
    void PUMPprocessor(char data[]);

    //STAT Message Processor
    void STATprocessor(char data[]);

    // SYNC Message Processor
    void SYNCprocessor(char data[]);

    // VALV Message Processor
    void VALVprocessor(char data[]);

    void primePumps();

    // Check the value of two sensors given the window
    int checkSensorWindow(int newSensor, int prevSensor, int window);

    struct txnRow{
    char code[TXN_CODE_LEN + 1];
    void (StateController::*func)(char[]);
    };

    QueueList<txnRow> txnTable;

};

Any idea what is wrong?

Answer 1

func is just a normal member of txnRow so you access it with ., not .*, e.g. txnTable[x].func.

To call this member function on, say, this, you would do something like:

(this->*(txnTable[x].func))(msg.data);