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Create an object of a class inside another class declaration in C++

Here, we are going to learn by a program how to create an object of a class inside another class declaration in C++ programming language?
Submitted by IncludeHelp, on September 15, 2018 [Last updated : March 01, 2023]

Creating an object of a class inside another class declaration

As we know that a class contains data members and member function, and an object can also be a data member for another class.

Logic to create an object of a class inside another class declaration

Here, in the given program, we are doing the same. We have a class named Marks that contains two data members rno - to store roll number and perc - to store the percentage of the student. We have another class named Students that contains two members name - to store the name of the student and objM - which is an object of Marks class.

In Students class there are two member functions:

1. readStudent() - To read the name of the student, and Here, we called readMarks() member function of Marks class by using objM - it will read roll number and percentage.
2. printStudent() - To print the name of the student, and Here, we called printMarks() member function of Marks class by using objM - it will print roll number and percentage.

C++ program to create an object of a class inside another class declaration

#include <iostream>
#include <string.h>

using namespace std;

class Marks {
private:
    int rno;
    float perc;

public:
    //constructor
    Marks()
    {
        rno = 0;
        perc = 0.0f;
    }

    //input roll numbers and percentage
    void readMarks(void)
    {
        cout << "Enter roll number: ";
        cin >> rno;
        cout << "Enter percentage: ";
        cin >> perc;
    }

    //print roll number and percentage
    void printMarks(void)
    {
        cout << "Roll No.: " << rno << endl;
        cout << "Percentage: " << perc << "%" << endl;
    }
};

class Student {
private:
    //object to Marks class
    Marks objM;
    char name[30];

public:
    //input student details
    void readStudent(void)
    {
        //Input name
        cout << "Enter name: ";
        cin.getline(name, 30);
        //input Marks
        objM.readMarks();
    }

    //print student details
    void printStudent(void)
    {
        //print name
        cout << "Name: " << name << endl;
        //print marks
        objM.printMarks();
    }
};

//main code
int main()
{
    //create object to student class
    Student std;
    std.readStudent();
    std.printStudent();

    return 0;
}

Output

Enter name: Amit Shukla
Enter roll number: 101
Enter percentage: 84.02
Name: Amit Shukla
Roll No.: 101
Percentage: 84.02%