Problem "mixing" class inheritance in C++ plugin and Unigine Script

[christian.wolf2]

Hi,

 

I am currently trying to export some classes from my C++ plugin to UnigineScript, inherit a class in UnigineScript and set it as variable in one of their base class. The C++ classes are defined as following:

class Task
{
protected:
	
	Task* parent;												//pointer to the parent of this task

	virtual int addChildToTask(Task* newChild) { return 0; };

public:

	Task();
	~Task();

	virtual int addChild(Task* newChild)						//adds an Child to this task
	{
		addChildToTask(newChild);
	}

};

class Sequence : public Task
{
protected:

	vector<Task*> children;

	virtual int addChildToTask(Task* newChild)
	{
		children.push_back(newChild);
	}

};

class LeafTask : public Task
{
public:

	virtual void executeLeafTask();
};

I exported all classes using "MakeExternClass" without any problems. In Unigine I inherit the LeafClass and tried to use my external classes:

class CustomLeafTask : public LeafTask
{
	(...)

public:

	void executeLeafTask();

};

(...)
//later in an world file:
init()
{		
	CustomLeafTask myLeaf = new CustomLeafTask();

	Sequence innerSequence = new Sequence();
	innerSequence.addChild(CustomLeafTask::cast(myLeaf.extern));		//use ::cast and .extern to use Unigine-Script class in extern plugin class - OK!

	Sequence outerSequence = new Sequence();
	outerSequence.addChild(innerSequence);					//crash "can't convert extern class to class Task* __ptr64"
}

The error occurs only, if I used the derived class I declared in UnigineScript. If I used the standard "Leaf-Class" the problem never appears. Using ::cast or .extern for the innerSequence aren't allowed because it is not defined. Is this behavior intended and are there any solutions for that?

 

Thanks in advance!

Christian

[unclebob]

Hi Christian!

 

It seems like a bug to me. Could you please show the export part of your code? Are you sure you don't forget to call interpreter->addBaseClass for all derived C++ classes?

[christian.wolf2]

On 17.7.2017 at 0:24 PM, unclebob said:

 Are you sure you don't forget to call interpreter->addBaseClass for all derived C++ classes?

 

Hi Bob,

 

actually not, because there aren't any hints in the documentation. :) I will try to implement that, can you please describe me how and when do I have to you use the addBaseClass()? Only if I use the function of the derived class without overwriting them or every time I derived a class from a base one regardeless of their use of a specific function?

[unclebob]

Hi Christian!

It's quite simple. Here's code sample:

// C++ part
class A {
public:
	virtual void baseMethod() const { Unigine::Log::message("A::baseMethod\n"); }
};

class B : public A {
public:
	void baseMethod() const override { Unigine::Log::message("B::baseMethod\n"); }
	void derivedMethod() const { Unigine::Log::message("B::derivedMethod\n"); }
};

void extendInterpreter() {
	auto a_class = Unigine::MakeExternClass<A>();
	a_class->addConstructor();
	a_class->addFunction("baseMethod", &A::baseMethod);

	auto b_class = Unigine::MakeExternClass<B>();
	b_class->addConstructor();
	b_class->addFunction("derivedMethod", &B::derivedMethod);
	b_class->addBaseClass(a_class);

	Unigine::Interpreter::addExternClass("A", a_class);
	Unigine::Interpreter::addExternClass("B", b_class);
}

// UnigineScript part
int init() {
	A foo = new A();
	foo.baseMethod();
	log.message("--\n");

	B bar = new B();
	bar.baseMethod();
	bar.derivedMethod();
	log.message("--\n");

	A baz = new B();
	baz.baseMethod();
	B(baz).derivedMethod();
	log.message("--\n");

	B qux = baz;
	qux.baseMethod();
	qux.derivedMethod();
	log.message("--\n");

	return 1;
}

 

[christian.wolf2]

Hi Bob,

 

sorry for my late reply. Indeed, your solution works for me, so thank you for that. Now, I am struggeling adding an UnigineScript-class I derived, to my C++ class. In my upper example I use the following function, which I exported it to UnigineScript:

virtual int addChildToTask(Task* newChild)
{
	children.push_back(newChild);
}

 

In my UnigineScript I used the function:

innerSequence.addChild(CustomLeafTask::cast(myLeaf.extern));	//use ::cast and .extern to use Unigine-Script class in extern plugin class - OK!

 

Unfortunately, the given (derived) task is always NULL if I add a Log-line in my C++ function (befor children.push_back()).

[christian.wolf2]

Hi,

are there any update to this? I added a short sample project to this post. Simply, create A as base class, Class B and C inherit from A. B has a vector, where I want to add childs as A class. The .dll file is imported as a plugin module to a sample project. I inherit a new class D in UnigineScript from C class. After that I want to add this class new D class to a B class. Even if I use the .extern classifier, the inherited object is NULL.

inheritance_example.rar

Edited October 15, 2017 by christian.wolf2

[silent]

Hi Christian,

Thanks for the test scene, I've send it to the dev team. Hope to get answer soon.

[moroz]

Hi Christian,

You have to call ancestor constructor in inherited class.

Example:

class D : C
{
public:

	D() : C() {}
  
	~D() {}
};

For details see this : https://developer.unigine.com/en/docs/2.5/code/uniginescript/language/oop#inheritance_c

 

But there is some problems. This way of constructor definition doesn't work:

void D::__D__() : C() 
{
}

 We will try to improve script behavior in this case, but for now it will work only that way.

[christian.wolf2]

Hi moroz,

 

thanks for the detailed feedback. I need indeed the improvement for the script behavior. So thanks for adding that. Do you already know, when it will be released?

[silent]

Hi Christian,

For now it's have lowest priority, so probably not this year.

Sorry for the inconvenience.

[christian.wolf2]

Hi silent,

thanks for the info. Do you know if of there are any workaround? I am currently working on a plugin where the user needs to be able to extend the classes I exported from C++. I'm not getting confident with the idea of adapt the system completely as UnigineScript. (I can P.M. you if you want to have more details about it)

 

Thanks a lot anyway

Christian