Parameterized Constructors in C++

Examples of Parameterized Constructor

Example 1

• C++

C++

#include <iostream>
#include <string>

using namespace std;

// Create a class.
class Birdhouse {
private:
int numHoles;
string color;

public:
// Parameterized constructor
Birdhouse(int numHoles, string color) {
this->numHoles = numHoles;
this->color = color;
}

void displayInfo() {
cout << "Number of holes: " << numHoles << endl;
cout << "Color: " << color << endl;
}
};

// Main function
int main() {
int numHoles;
string color;

cout << "Enter number of holes: ";
cin >> numHoles;

// Ignore the newline character in the input buffer
cin.ignore(); 
cout << "Enter color: ";
getline(cin, color);

Birdhouse myBirdhouse(numHoles, color);
myBirdhouse.displayInfo();

return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

Enter number of holes: 2
Enter color: Red
Number of holes: 2
Color: Red

Explanation

The code defines a `Birdhouse` class in C++ with a parameterized constructor that takes the number of holes and color as arguments. It also includes a `displayInfo()` method to show the birdhouse's details. In the `main()` function, user input for the number of holes and color is taken and used to create a `Birdhouse` object. The `displayInfo()` method is then called to display the birdhouse's information.

Example 2 

• C++

C++

#include <iostream>

class ExamResult {
private:
int eng, science, maths, obtained;
int max = 300;
float result;

public:
ExamResult(int a, int b, int c) {
maths = a;
eng = b;
science = c;
obtained = eng + science + maths;

// Perform division using float.
result = (static_cast<float>(obtained) / max) * 100; 
std::cout << result;
}
};

int main() {
ExamResult x1(90, 80, 99);
return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

89.6667

Explanation

The code defines a class ExamResult to represent an exam result. It has private variables for scores and the result. The constructor takes scores as parameters, calculates the total obtained marks and the result using floating-point division, and prints the result. In main(), an ExamResult object is created with scores 90, 80, and 99, displaying the calculated result.

Example 3

• C++

C++

#include<iostream>

class Point {
private:
    int x;
    int y;

public:
    // Parameterized constructor
    Point(int xCoord, int yCoord) : x(xCoord), y(yCoord) {}

    // Display the coordinates
    void display() {
        std::cout << "Point coordinates: (" << x << ", " << y << ")\n";
    }
};

int main() {
    // Create a Point object with specific coordinates
    Point point1(3, 7);

    // Display the coordinates using the member function
    point1.display();

    return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

Point coordinates: (3, 7)

Explanation

In this example, the Point class represents a point in a 2D space with x and y coordinates. The class has a parameterized constructor that initializes the x and y attributes with the provided values during object creation. In the main function, a Point object (point1) is created with coordinates (3, 7) using the parameterized constructor. The display member function is called to showcase the coordinates of the created point.

Example 4

• C++

C++

#include<iostream>
#include<string>

class Employee {
private:
    std::string name;
    int age;

public:
    // Parameterized constructor
    Employee(const std::string& empName, int empAge) : name(empName), age(empAge) {}

    // Display employee details
    void display() {
        std::cout << "Employee: " << name << ", Age: " << age << " years\n";
    }
};

int main() {
    // Create an Employee object with specific details
    Employee emp1("John Doe", 30);

    // Display employee details using the member function
    emp1.display();

    return 0;
}

You can also try this code with Online C++ Compiler

Run Code

Output

Employee: John Doe, Age: 30 years

Explanation

In this example, the Employee class represents an employee with a name and age. The class has a parameterized constructor that initializes the name and age attributes with the provided values during object creation. In the main function, an Employee object (emp1) is created with the name "John Doe" and age 30 using the parameterized constructor. The display member function is called to showcase the details of the created employee.

Difference between Default and Parametrized Constructor

Also see - Difference between argument and parameter

Frequently Asked Questions

What is parameterized constructor in C++?

In C++, a parameterized constructor is a constructor that takes parameters during the creation of an object. Unlike a default constructor, which has no parameters, a parameterized constructor allows you to initialize the object's properties with specific values provided as arguments.

What is parameterized constructor advantage?

The advantage of a parameterized constructor lies in its ability to customize object initialization. By accepting parameters, the constructor enables the creation of objects with specific attributes, providing flexibility and reusability in the code. This customization is particularly useful when different instances of the same class need to be initialized with distinct values.

Conclusion

In this article, we have discussed about the Parametrized Constructors in C++. We have discussed how does it works. We have also considered some examples to understand the concept of parameterized constructor. Then we have explained the differences between default and parameterized constructors for better understanding.

If you want to know more about “Parametrized Constructors in C++” and topics like this. In that case, refer to the following articles:

• Constructors and Destructors 
• Virtual Copy Constructor 
• Pure virtual destructor 
• Turbo C++
• Characteristics of OOPS

Refer to our guided paths on Code 360 to learn more about DSA, Competitive Programming, JavaScript, System Design, etc. Enrol in our courses and refer to the mock test and problems available. Take a look at the interview experiences and interview bundle for placement preparations.