Question

I have a simple example below that does not compile. i get the following warrning about const

Error message:
error C2662: ‘Cfoo::GetNum’ : cannot convert ‘this’ pointer from ‘const Cfoo’ to ‘Cfoo &’ Conversion loses qualifiers

class Cfoo 
{
    public:
        bool RunMe( const Cfoo * bar ) {
            int i = bar->GetNum() ; 
        }

        int GetNum() {
            return 7; 
        }
};   

int _tmain(int argc, _TCHAR* argv[])
{
    Cfoo a;

    Cfoo b;
    b.RunMe( &a); 

    return 0;
}

At first I though that had something to do with the GetNum not returning a const value. changing that did not seem to help.

What did I do wrong?, suggestion, hints, examples, links?

Answer 1

GetNum must promise it does not change the value of the object by making it a const member function

class Cfoo 
{
    public:
        bool RunMe( const Cfoo * bar ) {
            int i = bar->GetNum() ; 
        }

        int GetNum() const { // !!!
            return 7; 
        }
};