Why doesn't Unigine::Ptr<T> up cast automatically?

[namal.bambarasinghe_]

It looks like there is no way to cast the Unigine::Ptr to the base type.

Do we have to release the ownership everytime to get a NodePtr?

for example,

Unigine::NodePtr createNewNode(const std::string& name)
{
	auto dummy_node = Unigine::NodeDummy::create(name.c_str());
	dummy_node->release();
	return dummy_node->getNode();
}

Is there a way to remove the,

dummy_node->release();

function call?

Thanks in advance

[alexander]

Hi, namal.bambarasinghe!

Quote

Is there a way to remove the,

dummy_node->release();

function call?

No.

See what happens:
1) You create a node inside a function scope (createNewNode).
2) When a "return" is called, a dummy_node calls ~destructor(), which kills the node.
3) Because object was destroyed, the result that function is always equals to NULL.

The ->release() function resets the inner counter inside Ptr. After this, when ~destructor() is called, the object will not be deleted.
Please, do not forget to call the ->grab() after calling the createNewNode()! Otherwise, the object will never be deleted automatically (only when you call .destroy()).

Best regards,
Alexander

[namal.bambarasinghe_]

Hi Alexander,

I am trying to achive the following -

Unigine::NodePtr createNewNode(const std::string& name)
{
	return Unigine::NodeDummy::create(name.c_str());
}

The above is similar to std::shared_ptr behaviour as shown below,

class Base
{
};

class Derived : public Base
{
};

std::shared_ptr<Base> createDerived()
{
	return std::make_shared<Derived>();  
}

In the above code block, the smart pointer is automatically converted to the base type.

Is there any reason why the Unigine::Ptr doesn't allow this type of behaviour (allow up casting)?

[alexander]

Hi, Namal!

Quote

Is there any reason why the Unigine::Ptr doesn't allow this type of behaviour (allow up casting)?

Inside the engine you are manipulating not with the Node/NodeDummy, but with NodeInterface/NodeDummyInterface wrappers.  And they are not inherited directly from each other.
This is a bad design, unfortunately. A legacy that we can not remove yet.

So, you should use ::cast() or ->getNode()/->getObject() methods to convert one type to another. And ->release() / ->grab() methods to resolve "smart" pointers corner cases.

Best regards,
Alexander