Using C++ as a scripting language

gistfile1.txt

// one of the interfaces the script (DLL) code builds against.
// implemented in the engine runtime.
class ScriptInterface
{
public:
	virtual void Foo(void) = 0;
	virtual void Bar(void) = 0;
};



// in any of the scripts
class Script
{
public:
	void SetEnvironment(ScriptInterface* si)
	{
		m_interface = si;
	}

	void Update(void)
	{
		// can be called by only having a declaration of the interface.
		// we don't need to know anything about the concrete implementation of the interface.
		m_interface->Foo();
		m_interface->Bar();
	}

private:
	ScriptInterface* m_interface;
};


// export a single C function responsible for creating the script instance
extern "C" __declspec(dllexport) Script* CreateScript(void)
{
	Script* instance = new Script;
	return instance;
}




// on the engine side of things
class ScriptInterfaceImpl : public ScriptInterface
{
public:
	virtual void Foo(void)
	{
		// do whatever you want here. can use everything from the engine, because this is
		// compiled with the engine runtime code.
	}

	virtual void Bar(void)
	{
		// same here
	}
};


void InstantiateScript(void)
{
	// call an exported C function from the DLL to create the script, and set the environment
	Script* script = CreateScript();
	script->SetEnvironment(new ScriptInterfaceImpl);
}


// somewhere else, run the script every frame
script->Update(deltaTime);