using a function of a class in another class

[eoaneh]

Hi
i have a problem

i have a class with some functions and a constructor witch does a lot of things,
i want to use some of the functions in another class,
with inheritance the constructor stars working and i dont want this to happen
with friendship, it says it's the first use this function(i used class friendship and function friendship, both with a same result)

how can i do this?
again without the constructor of the first class starting.

this is a part of my code

class SignupCoourse;

  class SignUpProfessor: public SignUp
{
      friend class SignUpCourse;
protected:
          long long int PID;
public:
       SignUpProfessor();
       ~SignUpProfessor();
       void SetPID();
};
class SignUpCourse
{
protected:
         //some arguments 


public:
       SignUpCourse();
       ~SignUpCourse();
       //some functions
};
SignUpCourse::SignUpCourse()
{
                 CurrentFile.open("course.txt");
                 CurrentFile<<"\n";
                 //calling some functions
                 SetPID();
}

[keskiverto]

Line 5 introduces name SignUpCourse. Line 1 did mention SignupCourse.

However, whose SetPID() do you call? It is a member, so it requires an object of type SignUpProfessor. We can only guess that SetPID() modifies member PID of one specific object.

Furthermore, SetPID() is already public, so no friendship is required.