AngelScript: Registering a reference type

# Registering a reference type

The basic reference type should be registered with the following behaviours: asBEHAVE_FACTORY, asBEHAVE_ADDREF, and asBEHAVE_RELEASE.

    // Registering the reference type
    r = engine->RegisterObjectType("ref", 0, asOBJ_REF); assert( r >= 0 );

See also:
  The string add-on for an example of a reference type.

  Garbage collected objects, Class hierarchies, Registering a scoped reference type, and Registering a single-reference type for more advanced types.

## Factory function

The factory function is the one that AngelScript will use to instanciate objects of this type when a variable is declared. It is responsible for allocating and initializing the object memory.

The default factory function doesn't take any parameters and should return an object handle for the new object. Make sure the object's reference counter is accounting for the reference being returned by the factory function, so that the object is properly released when all references to it are removed.

    CRef::CRef()
    {
        // Let the constructor initialize the reference counter to 1
        refCount = 1;
    }

    CRef *Ref_Factory()
    {
        // The class constructor is initializing the reference counter to 1
        return new CRef();
    }

    // Registering the factory behaviour
    r = engine->RegisterObjectBehaviour("ref", asBEHAVE_FACTORY, "ref@ f()", asFUNCTION(Ref_Factory), asCALL_CDECL); assert( r >= 0 );

You may also register factory functions that take parameters, which may then be used when initializing the object.

The factory function must be registered as a global function, but can be implemented as a static class method, common global function, or a global function following the generic calling convention.

## Addref and release behaviours

    void CRef::Addref()
    {
        // Increase the reference counter
        refCount++;
    }

    void CRef::Release()
    {
        // Decrease ref count and delete if it reaches 0
        if( --refCount == 0 )
            delete this;
    }

    // Registering the addref/release behaviours
    r = engine->RegisterObjectBehaviour("ref", asBEHAVE_ADDREF, "void f()", asMETHOD(CRef,AddRef), asCALL_THISCALL); assert( r >= 0 );
    r = engine->RegisterObjectBehaviour("ref", asBEHAVE_RELEASE, "void f()", asMETHOD(CRef,Release), asCALL_THISCALL); assert( r >= 0 );

## Registering an uninstanciable reference type

Sometimes it may be useful to register types that cannot be instanciated by the scripts, yet can be interacted with. You can do this by registering the type as a normal reference type, but omit the registration of the factory behaviour. You can later register global properties, or functions that allow the scripts to access objects created by the application via object handles.

This would be used when the application has a limited number of objects available and doesn't want to create new ones. For example singletons, or pooled objects.