error with function

Hi,

I am trying to write a function but keep getting an error when I try to build. I'm not very experienced with c++ so I can't really figure out what the error means. The funcion is called like this:

Code:

nMarkerCount = netClient.GetMarkerCount();

and it looks like this:

Code:

int BMLClient::GetMarkerCount(void)
{
	if (!m_bConnected) return 0; //??

	long cmd = 3;
	if (!Send(&cmd, sizeof(cmd)))
	{
		std::cout << "Unable to send <get marker data> command" << std::endl;
		return false;
	}
	long count;
	if (!Recv(&count,sizeof(count)))
	{
		std::cout << "Unable to get marker count" << std::endl;
		return false;
	}
	m_nMarkerCount = count;
	m_buffer = new double[count*3];
	m_bConnected = true;
	return m_nMarkerCount;
}

I have declared it as public in the header file like this:

Code:

int GetMarkerCount(void);

The error that I get says: error C2662: 'BMLClient::GetMarkerCount' : cannot convert 'this' pointer from 'const BMLClient' to 'BMLClient &'


Can anyone tell from what I've posted what this error means? Thanks!

If the line in the header file is within a class, you're probably calling the function on a const object. How is netClient declared?

This probably isn't causeing that error but I can see two places where you're returning a bool instead of an int.

Send the class definition code if possible.

netClient is declared as:

Code:

protected:
	BMLClient netClient;

in this class:

Code:

class BMLDrawable: public osg::Drawable

i'm not sure what you mean by the class definition code....what else do i need to post?

Post your .h where your class is defined.

If your GetMarkerCount(void) function is defined within the BMLDrawable class you need to say...

Code:

int BMLDrawable::GetMarkerCount(void)
{
// stuff
}

ok hopefully this is the one

Code:

#pragma once
#include <winsock2.h>
#include "Vector3.h"

class BMLClient
{
public:
	BMLClient(void);
	virtual ~BMLClient(void);

	bool Connect(void);
	void Disconnect(void);
	bool isConnected(void) const { return m_bConnected; }
	int GetMarkerCount(void);
	void GetFrame(CVector3* buf) const;

protected:
	bool m_bConnected;				// true when connection to server established successfully
	int m_nMarkerCount;				// number of targets being tracked
	SOCKET m_socket;				// network socket connection to BML server
	double *m_buffer;				// buffer for frame data

	bool Send(void* buf, long size) const;
	bool Recv(void* buf, long size) const;
};

>> nMarkerCount = netClient.GetMarkerCount();

The place that the function call above is made is probably inside a BMLDrawable member function, right? If so, then is that member function const? Show the declaration of the function that contains the line above.

yup it's a const....here it is:

Code:

void BMLDrawable::drawImplementation (osg::State& state) const
{
	if (!netClient.isConnected()) return;

	nMarkerCount = netClient.GetMarkerCount();

	// draw a sphere at each joint
	glColor3fv(red);
	glEnable(GL_LIGHTING);
	for (int m=0; m<nMarkerCount; m++)
		GenSphere(frameData[m],BALL_RADIUS);
	
	// get next batch of frame data
	netClient.GetFrame(frameData);
}

There you go!

ok maybe this is stupid but i'm still not really sure how to fix this

Well.. what is happening, and Daved so cleverly guessed at, is that you are calling GetMarkerCount() which alters data members of your class from within a const member function named drawImplementation(). So...

drawImplementation() is really not a const function is it?

remove the const from both the declaration and definition and it should be ok

hmmm yea that's the first thing i tried but it's giving me more errors in this class:

Code:

class BMLDrawable: public osg::Drawable {
public:
	BMLDrawable();
	virtual ~BMLDrawable();

	virtual osg::Object* cloneType() const
	{
		return new BMLDrawable();
	}

	virtual osg::Object* clone(const osg::CopyOp&) const
	{
		return new BMLDrawable();
	}

	bool computeBound() const;
	virtual void drawImplementation(osg::State& state);

protected:
	BMLClient netClient;
	CVector3 *frameData;
	int nMarkerCount;
	GLuint nSphere;
	void GenSphere (CVector3 &center, GLfloat radius) const;
};

the errors say "error C2259: 'BMLDrawable' : cannot instantiate abstract class"

any clue what that means?

I think that instead you just solved a problem and it is now detecting another.

Does osg::Object have any pure virtual functions? And if so... are all of them being defined in BMLDrawable?

i'm not really sure what a pure virtual function is...how would i know?