Pointers to member functions within the same class (C++)? - c++

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);