I had two lessons in my recreation, Participant and ShootableObject. Each arrange as such:

class Participant : public RigidBody2D
{
personal:
    GDCLASS(Participant, RigidBody2D);
 ... implementation follows ...

class ShootableObject : public RigidBody2D
{
personal:
    GDCLASS(ShootableObject , RigidBody2D);
 ... implementation follows ...

And registered as such in my module:

void initialize_example_module(godot::ModuleInitializationLevel p_level)
{
    if (p_level != godot::MODULE_INITIALIZATION_LEVEL_SCENE)
    {
        return;
    }
    godot::ClassDB::register_class<godot::Participant>();
    godot::ClassDB::register_class<godot::ShootableObject>();
}

I wished to extract some widespread conduct from the 2 and created a 3rd class, as such:

class GravityBody2D : public RigidBody2D
{
personal:
    GDCLASS(GravityBody2D, RigidBody2D);

I then modified the inheritance of the opposite two:

class Participant : public GravityBody2D
{
personal:
    GDCLASS(Participant, GravityBody2D);
 ... implementation follows ...

And added it to the exports:

void initialize_example_module(godot::ModuleInitializationLevel p_level)
{
    if (p_level != godot::MODULE_INITIALIZATION_LEVEL_SCENE)
    {
        return;
    }
    godot::ClassDB::register_class<godot::Participant>();
    godot::ClassDB::register_class<godot::ShootableObject>();
    godot::ClassDB::register_class<godot::GravityBody2D>();
}

I now get an error that the lessons will not be discovered:

  Can not get class 'Participant'.
  Can not get class 'ShootableObject'.
  Can not get class 'ShootableObject'.

I can nevertheless see GravityBody2D within the node record:

How can I inherit my very own class?