OOP Basics

Hi, I am a first semester student, learning the OOPs basics. I need help for a program:

Code:

---

class Message{
public:
        void input();
        int output();
private:
        long token_number;// next token to be given to client

};

void Message::input()
{
        token_number = 1;
}

int Message::output()
{
        return token_number;
}

---

I dont know the right way to call these elements in the main()

int main(){
Message obj;

std::cout<< out_buffer<<obj.output()<<std::endl;//write the token number in the buffer
std::cout<<"Response received"<<++obj.input();//To update the input value and display
}

What is out_buffer?

I'm not sure what you're trying to achieve. Perhaps you could be more explicit in the requirements? However consider:

Code:

---

#include <iostream>

class Message {
public:
        void input();
        int output() const;

        Message& operator++() {
                ++token_number;
                return *this;
        }

private:
        long token_number {};
};

void Message::input() {
        token_number = 1;
}

int Message::output() const {
        return token_number;
}

int main() {
        Message obj;

        std::cout << "Response received " << (++obj).output() << '\n';
        std::cout << "Response received " << (++obj).output() << '\n';
}

---

which displays:

Code:

---

Response received 1
Response received 2

---

Why is there curly braces after the token_number ?

This is default value initialisation. If there's no value between the {} the variable is initialised to the default value for the type of the variable - which is 0 for long. It's good practice to initialise variables when they are defined. Variables of a class type should be initialised via their default constructor/constructors.

See https://en.cppreference.com/w/cpp/la...initialization