Compilation error Arduino C++ object library - c++

Question

I'm writing a C++ Arduino library for BlueTooth communication.
I implemented a mechanism in order to register a custom function to be executed when a certain byte comes from the BT connection. Pratically a sort of Java Hashmap.
Everything works fine but when I try to register a method of the library object in the constructor I got some compilation error which I cannot understand.
I'm using Arduino IDE 1.6.9 with Ubuntu 16.04 LTS 64bit. The board is an Arduino UNO.
Here below the code,
header:
#ifndef BlueHartwin_H
#define BlueHartwin_H
#include <SoftwareSerial.h>
#include <Streaming.h>;
#include <Arduino.h>
#define START_TX 254
#define STOP_TX 255
typedef void (* CmdFuncPtr) (); // this is a typedef to command functions
class BlueHartwin {
public:
BlueHartwin(byte bluetoothTx,byte bluetoothRx,long baudRate);
~BlueHartwin();
boolean registerCmd(byte id,CmdFuncPtr cmdFuncPtr);
boolean unRegisterCmd(byte id,CmdFuncPtr cmdFuncPtr);
boolean runCmd(byte id);
void setDataLength(byte dataLength);
byte getDataLength();
byte getIncomingByte();
void txSwitchOff(void);
void txSwitchOn(void);
bool isTx();
boolean available();
boolean read();
void write(byte data,boolean endLine);
private:
CmdFuncPtr setOfCmds[255];
byte mDataLength;
bool tx;
byte incomingByte;
};
#endif
body:
#include "BlueHartwin.h";
/*
* Reserved command IDs:
* 14,
* 15
*/
SoftwareSerial bluetooth(7,8);
BlueHartwin::BlueHartwin(byte bluetoothTx,byte bluetoothRx,long baudRate){
bluetooth = SoftwareSerial(bluetoothTx,bluetoothRx);
bluetooth.begin(baudRate);
for (int i=0;i<=255;i++) {
setOfCmds[i]=NULL;
}
tx=false;
registerCmd(14,&txSwitchOff);
registerCmd(15,&txSwitchOn);
}
BlueHartwin::~BlueHartwin(){
}
boolean BlueHartwin::registerCmd(byte id,CmdFuncPtr cmdFuncPtr){
if (setOfCmds[id]==NULL) {
setOfCmds[id]=cmdFuncPtr;
return true;
} else return false;
}
boolean BlueHartwin::unRegisterCmd(byte id,CmdFuncPtr cmdFuncPtr){
setOfCmds[id]=NULL;
return true;
}
boolean BlueHartwin::runCmd(byte id){
if (setOfCmds[id]!=NULL) {
setOfCmds[id]();
return true;
} else return false;
}
void BlueHartwin::setDataLength(byte dataLength) {
mDataLength=dataLength;
}
byte BlueHartwin::getDataLength(){
return mDataLength;
}
byte BlueHartwin::getIncomingByte(){
return incomingByte;
}
boolean BlueHartwin::isTx(){
return tx;
}
void BlueHartwin::txSwitchOff(void){
tx=false;
Serial<<"now tx is "<<tx<<endl;
}
void BlueHartwin::txSwitchOn(void){
tx=true;
Serial<<"now tx is "<<tx<<endl;
}
boolean BlueHartwin::available(){
return bluetooth.available();
}
boolean BlueHartwin::read(){
if (bluetooth.available()>0)
{
incomingByte=bluetooth.read();
Serial << "Incoming byte " << incomingByte<<endl;
return runCmd(incomingByte);
}
return false;
}
void BlueHartwin::write(byte data,boolean endLine){
if (tx) {
if (endLine) bluetooth << data << endl;
else bluetooth<<data;
}
}
error:
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp: In constructor 'BlueHartwin::BlueHartwin(byte, byte, long int)':
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:21:18: error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function. Say '&BlueHartwin::txSwitchOff' [-fpermissive]
registerCmd(14,&txSwitchOff);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:21:29: error: no matching function for call to 'BlueHartwin::registerCmd(int, void (BlueHartwin::*)())'
registerCmd(14,&txSwitchOff);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:21:29: note: candidate is:
In file included from /home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:1:0:
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: boolean BlueHartwin::registerCmd(byte, CmdFuncPtr)
boolean registerCmd(byte id,CmdFuncPtr cmdFuncPtr);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: no known conversion for argument 2 from 'void (BlueHartwin::*)()' to 'CmdFuncPtr {aka void (*)()}'
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:22:18: error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function. Say '&BlueHartwin::txSwitchOn' [-fpermissive]
registerCmd(15,&txSwitchOn);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:22:28: error: no matching function for call to 'BlueHartwin::registerCmd(int, void (BlueHartwin::*)())'
registerCmd(15,&txSwitchOn);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:22:28: note: candidate is:
In file included from /home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:1:0:
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: boolean BlueHartwin::registerCmd(byte, CmdFuncPtr)
boolean registerCmd(byte id,CmdFuncPtr cmdFuncPtr);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: no known conversion for argument 2 from 'void (BlueHartwin::*)()' to 'CmdFuncPtr {aka void (*)()}'
exit status 1
Errore durante la compilazione per la scheda Arduino/Genuino Uno.
If I change in the constructor the rows:
registerCmd(14,&txSwitchOff);
registerCmd(15,&txSwitchOn);
to
registerCmd(14,&BlueHartwin::txSwitchOff);
registerCmd(15,&BlueHartwin::txSwitchOn);
I got this error:
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp: In constructor 'BlueHartwin::BlueHartwin(byte, byte, long int)':
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:21:42: error: no matching function for call to 'BlueHartwin::registerCmd(int, void (BlueHartwin::*)())'
registerCmd(14,&BlueHartwin::txSwitchOff);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:21:42: note: candidate is:
In file included from /home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:1:0:
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: boolean BlueHartwin::registerCmd(byte, CmdFuncPtr)
boolean registerCmd(byte id,CmdFuncPtr cmdFuncPtr);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: no known conversion for argument 2 from 'void (BlueHartwin::*)()' to 'CmdFuncPtr {aka void (*)()}'
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:22:41: error: no matching function for call to 'BlueHartwin::registerCmd(int, void (BlueHartwin::*)())'
registerCmd(15,&BlueHartwin::txSwitchOn);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:22:41: note: candidate is:
In file included from /home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.cpp:1:0:
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: boolean BlueHartwin::registerCmd(byte, CmdFuncPtr)
boolean registerCmd(byte id,CmdFuncPtr cmdFuncPtr);
^
/home/paolo/ARDUINO/arduino-1.6.9/libraries/BlueHartwin/BlueHartwin.h:19:10: note: no known conversion for argument 2 from 'void (BlueHartwin::*)()' to 'CmdFuncPtr {aka void (*)()}'
exit status 1
Errore durante la compilazione per la scheda Arduino/Genuino Uno.
Thanks in advance for help!

Answer 1

Mate, your txSwitchOn/Off methods are instance ones - they require a this to work fine.
On the other side, your CmdFuncPtr is the definition of a function that doesn't depend on anything.
How many such devices (to be supported by your library) is Arduino assumed to handle at any one time?
If it's a single one, then declare everything static, rename the constructot to "static void init() and the destructor to "static void disconnect()", etc. You will have the class acting as just a naming context for your functions (all static).