C++ Class Constructor With Parameters Example

4 min read Jul 01, 2024

C++ Class Constructor with Parameters Example

In C++, a constructor is a special member function that is automatically called when an object of a class is created. It initializes the data members of the object. A constructor with parameters allows you to pass values to the object during its creation, providing flexibility and control over its initial state.

Here's a breakdown of how to use constructors with parameters:

Example: A Student Class

Let's define a simple Student class with data members for name, rollNumber, and age:

#include 
#include 

using namespace std;

class Student {
public:
    // Constructor with parameters
    Student(string name, int rollNumber, int age) {
        this->name = name;
        this->rollNumber = rollNumber;
        this->age = age;
    }

    // Member function to display student details
    void displayDetails() {
        cout << "Name: " << name << endl;
        cout << "Roll Number: " << rollNumber << endl;
        cout << "Age: " << age << endl;
    }

private:
    string name;
    int rollNumber;
    int age;
};

Explanation:

Constructor declaration:
- The constructor Student(string name, int rollNumber, int age) takes three parameters: name (a string), rollNumber (an integer), and age (an integer).
- The constructor name is the same as the class name.
- It has no return type, not even void.
Initialization:
- Inside the constructor, we use this-> to access the private data members name, rollNumber, and age of the object.
- The constructor assigns the values of the parameters to the corresponding data members.
Member function displayDetails():
- This function prints the student's details to the console.

Creating and Using Objects

Now, let's create Student objects and use the constructor to initialize them:

int main() {
    // Creating objects with different values using the constructor
    Student student1("Alice", 101, 18);
    Student student2("Bob", 102, 19);

    // Displaying details of each student
    cout << "Student 1 details:\n";
    student1.displayDetails();

    cout << "\nStudent 2 details:\n";
    student2.displayDetails();

    return 0;
}

Output:

Student 1 details:
Name: Alice
Roll Number: 101
Age: 18

Student 2 details:
Name: Bob
Roll Number: 102
Age: 19

Key Points

Constructors with parameters are essential for creating objects with specific initial values.
The order of parameters in the constructor call must match the order of parameters in the constructor definition.
You can have multiple constructors in a class, each with different parameters, allowing for different initialization scenarios.
Constructors ensure that objects are created in a consistent and initialized state.

By using constructors with parameters, you enhance the flexibility and control over how your objects are created, promoting clean code and efficient initialization.

C++ Class Constructor With Parameters Example