passing const ptr argument

[Anthony]

Hi,
I want to write protect an argument that is passed by reference.
But I still want to be able to call members of that argument.
E.g. code (bottum) will gives the following compiler error:
writeProtEvt.cpp: In member function `virtual void A::print(const B*)':
writeProtEvt.cpp:24: error: passing `const B' as `this' argument of `virtual
void B::print()' discards qualifiers

Can anyone explain how to do this the right way?

thanks in advance,
Anthony Lansbergen

// -------------------------------------------------------------------------
---
#include <ostream.h>
Class B
{
public:
virtual void print()
{
cout << "printB" << std::endl;
}
};

class A
{
public:
virtual void print(const B* b)
{
cout << "printA" << std::endl;
b->print();
}
};

main()
{
cout << "test" << std::endl;
A* a;
B* b;
a = new A();
b = new B();
a->print(b);
}

[Gianni Mariani]

Anthony wrote:

Hi,
I want to write protect an argument that is passed by reference.
But I still want to be able to call members of that argument.
E.g. code (bottum) will gives the following compiler error:
writeProtEvt.cpp: In member function `virtual void A::print(const B*)':
writeProtEvt.cpp:24: error: passing `const B' as `this' argument of `virtual
void B::print()' discards qualifiers

Can anyone explain how to do this the right way?

thanks in advance,
Anthony Lansbergen

// -------------------------------------------------------------------------
---
#include <ostream.h>
Class B
{
public:
virtual void print() Try this :

virtual void print() const
{
cout << "printB" << std::endl;
}

Note the const at the end of the function decl. This indicates that the
"this" parameter to the function is const.
{
cout << "printB" << std::endl;
}
};

class A
{
public:
virtual void print(const B* b)
{
cout << "printA" << std::endl;
b->print();
}
};

main()
{
cout << "test" << std::endl;
A* a;
B* b;
a = new A();
b = new B();
a->print(b);
}

[Ali Cehreli]

On Wed, 11 Aug 2004 10:06:54 +0200, Anthony wrote:

I want to write protect an argument that is passed by reference.
But I still want to be able to call members of that argument.
This means that you can call only const member functions of those
objects.
E.g. code (bottum) will gives the following compiler error:
writeProtEvt.cpp: In member function `virtual void A::print(const B*)':
writeProtEvt.cpp:24: error: passing `const B' as `this' argument of `virtual
void B::print()' discards qualifiers

Can anyone explain how to do this the right way?

thanks in advance,
Anthony Lansbergen

// -------------------------------------------------------------------------
---
#include <ostream.h>
Class B
{
public:
virtual void print()
{
cout << "printB" << std::endl;
}
};

class A
{
public:
virtual void print(const B* b)
{
cout << "printA" << std::endl;
b->print();
}
};
Both of those member functions should be declared as const because
they don't modify the object:

virtual void print() const // <---
{
/* ... */
}

main()

main returns 'int' and it must be specified:

int main()

Ali