Passing an object to a method CPP C-CodePudding

I'm still learning C so go easy on me. Is there a way I can pass an object to a method without specifying an object? I'm probably butchering the terms so ill show code.

class Student
{private:
    std::string Name;
    float GPA;
    char Sex;
    int Absentee;
    int *Data ;
public:
    std::string GetName();
    float GetGPA();
    char GetSex();
    int GetAbsentee();
    void SetData(int);
    int GetData();
    int *GetDataAddr();

    //Methods
    void DisplayStudent(Student);

void Student::DisplayStudent(Student Stud)
{
    std::cout << "___________________________________" << std::endl;
    std::cout << "Name     :" << Stud.GetName() << std::endl;
    std::cout << "GPA      :" << Stud.GetGPA() << std::endl;
    std::cout << "Sex      :" << Stud.GetSex() << std::endl;
    std::cout << "Absentee :" << Stud.GetAbsentee() << std::endl;
    std::cout << "Data     :" << Stud.GetData() << std::endl;
    std::cout << "Data Add :" << Stud.GetDataAddr() << std::endl;
    std::cout << "___________________________________" << std::endl;
}



int main() {

    
    Student Spike("Spike", 3.9f, 'M', 43,55);
    * Compiles fine: Spike.DisplayStudent(Spike);
    * DOSNT Compile: Student DisplayStudent(Spike);
    * C   a nonstatic member reference must be relative to a specific object*
    return 0;

}

So the question I have is at least with this method, why do I need to specify or rather, what is the purpose of "Spike" in "Spike.DisplayStudent(.....)"? Student::Display(.....) makes far more sense to me.

CodePudding user response：

If your Student::DisplayStudent is designed to display information for the student who is represented by that class instance, you don't need to pass Student Stud at all, just use member variables.

If however it is designed to display info for ANY student - you can make it a static member, or a free-standing function.

CodePudding user response：

If you want the member function DisplayStudent to display the information for the very instance of Student on which the function is called, you do not need to pass a Student as an argument.

class Student {
public:
    // The getter methods should be `const`, since calling them does not change
    // the `Student`:
    const std::string& GetName() const; // return a `const&` to avoid unecessary copying
    void DisplayStudent() const;        // No `Student` argument, like in `GetName()`
    // ...
};

void Student::DisplayStudent() const {
    std::cout << "___________________________________\n"
                 "Name     :" << GetName() << "\n"
                 "GPA      :" << GetGPA() << "\n"
                 "Sex      :" << GetSex() << "\n"
                 "Absentee :" << GetAbsentee() << "\n"
                 "Data     :" << GetData() << "\n"
                 "Data Add :" << GetDataAddr() << "\n"
                 "___________________________________\n";
}

You also do not need to call getter methods in DisplayStudent() since you have access to the private member variables and do not need to do any calculations before returning the result.

Usage example (if the appropriate constructor exists as you've indicated):

int main() {
    Student Spike("Spike", 3.9f, 'M', 43,55);
    Spike.DisplayStudent(); // no instance passed as an argument
}