Introduction
In C++, an array of objects allows you to manage and manipulate multiple instances of a class efficiently. By creating an array of objects, you can easily access and modify the attributes and behaviors of each object within the array. This approach is particularly useful in scenarios where you need to handle collections of related entities, such as students, employees, or products.
Defining a Class and Creating an Array of Objects
To define an array of objects, you first create a class with the necessary members and member functions. Then, you create an array of that class type.
Example: Defining a Class and Creating an Array
#include <iostream>
using namespace std;
class Student {
public:
string name;
int age;
double grade;
// Constructor
Student(string n, int a, double g) : name(n), age(a), grade(g) {}
// Member function to display student details
void display() {
cout << "Name: " << name << ", Age: " << age << ", Grade: " << grade << endl;
}
};
int main() {
// Create an array of Student objects
Student students[3] = {
Student("Aarav", 20, 88.5),
Student("Siya", 21, 92.0),
Student("Rohan", 19, 75.0)
};
// Print student data
for (int i = 0; i < 3; i++) {
students[i].display();
}
return 0;
}
Output
Name: Aarav, Age: 20, Grade: 88.5
Name: Siya, Age: 21, Grade: 92
Name: Rohan, Age: 19, Grade: 75
Explanation
- The
Student
class is defined withname
,age
, andgrade
members and a constructor to initialize these members. - A member function
display
is defined to print the student’s details. - An array of
Student
objects,students
, is created and initialized with data for three students. - A loop iterates through the array, calling the
display
function for each student to print their details.
Practical Examples
Example 1: Calculating the Average Grade
#include <iostream>
using namespace std;
class Student {
public:
string name;
int age;
double grade;
Student(string n, int a, double g) : name(n), age(a), grade(g) {}
void display() {
cout << "Name: " << name << ", Age: " << age << ", Grade: " << grade << endl;
}
};
double calculateAverageGrade(Student students[], int size) {
double total = 0;
for (int i = 0; i < size; i++) {
total += students[i].grade;
}
return total / size;
}
int main() {
Student students[3] = {
Student("Aarav", 20, 88.5),
Student("Siya", 21, 92.0),
Student("Rohan", 19, 75.0)
};
int size = 3;
double averageGrade = calculateAverageGrade(students, size);
cout << "Average Grade: " << averageGrade << endl;
return 0;
}
Output
Average Grade: 85.1667
Explanation
- The
calculateAverageGrade
function takes an array ofStudent
objects and the array size as arguments. - It calculates and returns the average grade of the students.
- The
main
function initializes the array, calls thecalculateAverageGrade
function, and prints the average grade.
Example 2: Finding the Youngest Student
#include <iostream>
using namespace std;
class Student {
public:
string name;
int age;
double grade;
Student(string n, int a, double g) : name(n), age(a), grade(g) {}
void display() {
cout << "Name: " << name << ", Age: " << age << ", Grade: " << grade << endl;
}
};
int findYoungestStudent(Student students[], int size) {
int youngestIndex = 0;
for (int i = 1; i < size; i++) {
if (students[i].age < students[youngestIndex].age) {
youngestIndex = i;
}
}
return youngestIndex;
}
int main() {
Student students[3] = {
Student("Aarav", 20, 88.5),
Student("Siya", 21, 92.0),
Student("Rohan", 19, 75.0)
};
int size = 3;
int youngestIndex = findYoungestStudent(students, size);
cout << "Youngest Student: " << students[youngestIndex].name
<< ", Age: " << students[youngestIndex].age << endl;
return 0;
}
Output
Youngest Student: Rohan, Age: 19
Explanation
- The
findYoungestStudent
function takes an array ofStudent
objects and the array size as arguments. - It finds and returns the index of the youngest student.
- The
main
function initializes the array, calls thefindYoungestStudent
function, and prints the details of the youngest student.
Example 3: Sorting Students by Grade
#include <iostream>
#include <algorithm>
using namespace std;
class Student {
public:
string name;
int age;
double grade;
Student(string n, int a, double g) : name(n), age(a), grade(g) {}
void display() {
cout << "Name: " << name << ", Age: " << age << ", Grade: " << grade << endl;
}
};
// Comparator function to sort students by grade
bool compareGrades(Student a, Student b) {
return a.grade > b.grade; // Sort in descending order
}
int main() {
Student students[3] = {
Student("Aarav", 20, 88.5),
Student("Siya", 21, 92.0),
Student("Rohan", 19, 75.0)
};
int size = 3;
// Sort the students by grade
sort(students, students + size, compareGrades);
// Print sorted student data
for (int i = 0; i < size; i++) {
students[i].display();
}
return 0;
}
Output
Name: Siya, Age: 21, Grade: 92
Name: Aarav, Age: 20, Grade: 88.5
Name: Rohan, Age: 19, Grade: 75
Explanation
- The
compareGrades
function is a comparator function used to sort students by their grades in descending order. - The
sort
function from the<algorithm>
header sorts the array of students using thecompareGrades
function. - The sorted array is printed, showing students ordered by their grades.
Conclusion
An array of objects in C++ provides a structured way to manage and manipulate collections of instances of a class. This chapter covered the basics of defining a class and creating an array of objects, along with practical examples demonstrating how to calculate the average grade, find the youngest student, and sort students by grade. Understanding how to use arrays of objects effectively is essential for organizing and processing complex data in C++ programs.