Extensions: Extend a macro without overlay - pack/unpack

I have a class that implements SysPackable. When I extend this class I want also to extend the list of variables in the macro.

Note: in Ax 2012 you don’t have SysPackExtensions.
otherwise see here: https://docs.microsoft.com/en-us/dynamics365/fin-ops-core/dev-itpro/extensibility/extend-runbase-class

class EF_SysPackableTrial implements SysPackable
{
    Description description;
    str myString;

    #define.CurrentVersion(1)
    #define.version1(1)
    #localmacro.CurrentList
    description,
    myString
    #endmacro
}

public container pack()
{
    return [#CurrentVersion, #CurrentList];
}

public boolean unpack(container packedClass)
{
    int version     = runbase::getVersion(packedClass);

    switch (version)
    {
        case #CurrentVersion:
            [version,#CurrentList] = packedClass;
            return true;
        default :
            return false;
    }

    return false;
}

public static EF_SysPackableTrial create(container _pack)
{
    EF_SysPackableTrial cl = new EF_SysPackableTrial();

    cl.unpack(_pack);
    return cl;
}

public Description parmDescription(Description _description = description)
{
    description = _description;

    return description;
}

public str parmMyString(str _myString = myString)
{
    myString = _myString;

    return myString;
}

in the extend class I modified the pack and unpack methods

class EF_SysPackableTrialExtend extends EF_SysPackableTrial
{
    Name name;

    #define.CurrentVersion(1)
    #define.version1(1)
    #localmacro.CurrentList1
    name
    #endmacro
}

public container pack()
{
    container ret;
    
    ret = [#CurrentVersion, [#CurrentVersion, #CurrentList], [#CurrentVersion, #CurrentList1]];
    
    return ret;
}

public boolean unpack(container packedClass)
{
    int version = SysOperationHelper::getVersion(packedClass);

    switch (version)
    {
        case #CurrentVersion:
            [version,#CurrentList] = conPeek(packedClass,2);
            [version,#CurrentList1] = conPeek(packedClass,3);
            return true;
        default :
            return false;
    }

    return false;
}

public static EF_SysPackableTrialExtend create(container _pack)
{
    EF_SysPackableTrialExtend cl = new EF_SysPackableTrialExtend();

    cl.unpack(_pack);
    return cl;
}

public Name parmName(Name _name = name)
{
    name = _name;

    return name;
}

and here a simple job to prove it works fine:

static void EF_SysPackableTrialExtend(Args _args)
{
    EF_SysPackableTrialExtend EF_SysPackableTrialExtend, sysPackableTrial1;

    EF_SysPackableTrialExtend = new EF_SysPackableTrialExtend();
    EF_SysPackableTrialExtend.parmDescription('ciao1');
    EF_SysPackableTrialExtend.parmMyString('ciao2');
    EF_SysPackableTrialExtend.parmName('pp');

    sysPackableTrial1 = EF_SysPackableTrialExtend::create(EF_SysPackableTrialExtend.pack());

    info(sysPackableTrial1.parmDescription());
    info(sysPackableTrial1.parmMyString());
    info(sysPackableTrial1.parmName());
}

I posted this sample also on the forum https://community.dynamics.com/ax/f/microsoft-dynamics-ax-forum/380610/extensions-extend-a-macro-without-overlay---pack-unpack-in-ax-2012