Templates and Array of structs that contain pointer to method in class - c++

Question

I am trying to create a class that defines an array of command structs, each of which has two CHAR variables, one CHAR*, one INT and a pointer to a void function that accepts two CHAR arguments. There will be multiple instances of this array, each in a different class. I feel like I am close, but missing something critical. The Arduino GNU compiler seems to agree that I am missing something. Here's the code (with modifications as per Bo R);
<<<<<<<<<< Commands.h >>>>>>>>>>>>>>>>>
#pragma once
//template <class T>
class Commands {
public:
typedef void ( Commands::*FunctionPointer )( char, char );
struct command {
char sel;
char act;
char const *desc;
FunctionPointer funcPtr;
};
command myCommands [2] = {
command { 'a','?',"FOO", &Commands::foo },
command { 'b','x',"BAR", &Commands::bar },
};
int cmdSize = sizeof ( myCommands ) / sizeof ( myCommands [0] );
void foo ( char sel, char act ) {
show ( { sel }, { act } );
}
void bar ( char sel, char act ) {
show ( { sel }, { act } );
}
void show ( char sel, char act ) {
Serial.print ( "SEL = " );
Serial.print ( sel );
Serial.print ( " ACT = " );
Serial.println ( act );
}
void execute ( char sel, char act ) {
for (int i = 0; i < cmdSize; i++) {
if (myCommands [i].sel == sel && myCommands [i].act == act) {
Serial.println ( myCommands [i].desc );
( this->*myCommands [i].funcPtr )( sel, act );
return;
}
}
Serial.print ( F ( "Unknown SEL/ACT Pair:" ) );
Serial.print ( sel );
Serial.print ( '/' );
Serial.println ( act );
}
};
<<<<<<<<<< StructArray.ino >>>>>>>>>>>>>>>>>
#include "Commands.h"
Commands cmd;
void setup() {
Serial.begin ( 115200 );
Serial.println ( "EXECUTING:" );
cmd.execute ( 'a', '?' );
cmd.execute ( 'b', '?' );
cmd.execute ( 'b', 'x' );
Serial.println ( "DONE" );
}
void loop(){}
If I refactor Commands into Template.h and Foo.h (as below), I get four compile errors that I don't understand how to fix:
Severity Code Description File Line
Error error: invalid use of template-name 'Template' without an argument list D:\Documents\Arduino\StructArray\Foo.h 6
Error error: 'myCommands' was not declared in this scope D:\Documents\Arduino\StructArray\Foo.h 11
Error error: 'myCommands' was not declared in this scope D:\Documents\Arduino\StructArray\Foo.h 11
Error error: invalid use of template-name 'Foo' without an argument list D:\Documents\Arduino\StructArray\StructArray.ino 7
Here is the code for Template.h:
#pragma once
template <class T>
class Template {
public:
typedef void ( T::*FunctionPointer )( char, char );
struct command {
char sel;
char act;
char const *desc;
FunctionPointer funcPtr;
};
void show ( char sel, char act ) {
Serial.print ( "SEL = " );
Serial.print ( sel );
Serial.print ( " ACT = " );
Serial.println ( act );
}
void execute ( char sel, char act, int cmdSize ) {
for (int i = 0; i < cmdSize; i++) {
if (T::myCommands[i].sel == sel && T::myCommands [i].act == act) {
Serial.println ( T::myCommands [i].desc );
( this->*T::myCommands [i].funcPtr )( sel, act );
return;
}
}
Serial.print ( F ( "Unknown SEL/ACT Pair:" ) );
Serial.print ( sel );
Serial.print ( '/' );
Serial.println ( act );
}
};
And Foo.h:
#pragma once
#include "Template.h"
template<class T>
class Foo {
public:
Template::command myCommands [2] = {
command { 'a','?',"FOO-A", &Foo::foo },
command { 'b','x',"FOO-B", &Foo::bar },
};
int cmdSize = sizeof ( myCommands ) / sizeof ( myCommands [0] );
void foo ( char sel, char act ) {
show ( { sel }, { act } );
}
void bar ( char sel, char act ) {
show ( { sel }, { act } );
}
};

Answer 1

If I start you out on the non-templated version, you will see that you need to make some changes.
class Commands {
public:
typedef void ( Commands::*FunctionPointer )( char, char );
struct command {
char sel;
char act;
char const *desc;
FunctionPointer funcPtr;
};
command myCommands [2] = {
{ 'a','?',"FOO", &Commands::foo },
{ 'b','x',"BAR", &Commands::bar }
};
int cmdSize = sizeof ( this->myCommands ) / sizeof ( this->myCommands [0] );
void foo ( char sel, char act ) {
char buf[2] = {sel};
Serial.println ( buf );
}
void bar ( char sel, char act ) {
char buf[2] = { sel };
Serial.println ( buf );
}
void execute ( char sel, char act ) {
for (int i = 0; i < cmdSize; i++) {
if (myCommands [i].sel == sel && myCommands [i].act == act) {
Serial.println ( myCommands [i].desc );
(this->*myCommands [i].funcPtr)( sel, act );
}
}
}
};
Once that is solved you can attack the templating (which I didn't see the purpose right now in this example since the foo and bar were part of the template class.)