C/C++ :: Finding The Right Class Hierarchy Implementation?

code:

    class BM_FONT_CALL BMfont  {
    public:  
    BMfont();
    ~BMfont();  
    bool Load(const std::string& fontName);
    void Print(float x, float y);  
    class BM_FONT_CALL BMstring : public std::string
 
[code]....

How can I do `BMstring` have an access to `BMfont`'s members, as if `BMstring` will not inherit `BMfont`'s members? For example, if I do this:

    BMfont::BMstring text;
    text.scale //I don't want this  

What I want to do here is, I want the `BMstring::Compile()` to have an access to `BMfont` with no any instance of `BMfont` inside `BMstring`.

Or what if I do this:

    class BM_FONT_CALL BMstring : public std::string {  
        std::function<void (void)> func;  
    public:  
        BMstring() { func = BMfont::Compile(); }  
    }  

By making the `Compile()` member of `BMfont`.But this won't compile. How can I achieve this?