C++ How to access private static variable in another class

Question

I am trying to access a private static variable (*PhysicsEngine::_world->setDebugDrawer(&debugDraw);*) from another class.

First class:

namespace GameEngine
{
    class PhysicsEngine
    {
    private:
        // Pointer to Bullet's World simulation
        static btDynamicsWorld* _world;

Second class:

bool Game::initialise()
    {
        _device = irr::createDevice(irr::video::EDT_OPENGL,
                                    _dimensions,
                                    16,
                                    false,
                                    false,
                                    false,
                                    &inputHandler);

        if(!_device)
        {
            std::cerr << "Error creating device" << std::endl;
            return false;
        }
        _device->setWindowCaption(_caption.c_str());

    //////////////
    DebugDraw debugDraw(game._device);
    debugDraw.setDebugMode(
    btIDebugDraw::DBG_DrawWireframe |
    btIDebugDraw::DBG_DrawAabb |
    btIDebugDraw::DBG_DrawContactPoints |
    //btIDebugDraw::DBG_DrawText |
    //btIDebugDraw::DBG_DrawConstraintLimits |
    btIDebugDraw::DBG_DrawConstraints //|
    );
    PhysicsEngine::_world->setDebugDrawer(&debugDraw);

If I make _world public I get Unhandled exception at 0x00EC6910 in Bullet01.exe: 0xC0000005: Access violation reading location 0x00000000.

if you wanna reach it from outside why not make it public then? — fatihk
– fatihk, Commented Apr 10, 2013 at 13:56
Instead write a public method in PhysicsEngine that takes debugDraw and would call the setDebugDrawer on _world and set the debugDraw. — Abhijit-K
– Abhijit-K, Commented Apr 10, 2013 at 14:07

Rush · Accepted Answer · 2013-04-10 13:58:29Z

1

Expose some static function in the Physics Engine class which returns a reference or pointer to the private static variable _world then call that static function.

PhysicsEngine::getWorld()->setDebugDrawer(&debugDraw);

Expose the below method

static btDynamicsWorld* getWorld() { return _world; }

answered Apr 10, 2013 at 13:58

Rush

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3 Comments

Andrew Uknown Over a year ago

Thank you that worked... however I still get the access violation. I probably should look more into Bullet Physics.

Rush Over a year ago

What access violation do you get? Did you put the above method under public access?

Andrew Uknown Over a year ago

I realised my stupidity and placed it into Private, I thought worked but I just don't get the access violation. Now I get error C2248: 'GameEngine::PhysicsEngine::getWorld' : cannot access private member declared in class 'GameEngine::PhysicsEngine'

paper.plane · Accepted Answer · 2013-04-10 13:57:07Z

0

Declare that class as Friend in this class. Then the member functions of that class can access this private static member.

answered Apr 10, 2013 at 13:57

paper.plane

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