Constructor
Constructor is a special kind of member method which never return a value. It is used to initialize an object.
- Constructor name is the class name.
- It is self-executed when an object is created or initialize.
- Constructor should be public.
How to use constructor?
#include <iostream>
using namespace std;
class Student {
public:
string studentName;
int sAge;
// constructor
Student(string name, int age) {
studentName = name;
sAge = age;
}
void printInfo() {
cout << "Student name is : " << studentName << endl;
cout << "Student age is : " << sAge << endl;
}
};
int main(int argc, char const *argv[]) {
Student s1("Online Vidyalay", 32);
// calling method
s1.printInfo();
return 0;
}
// output
// Student name is : Online Vidyalay
// Student age is : 32Types of constructor
There are main three types of constructor in c++ programming
- Default constructor
- Parameterized constructor
- Copy constructor
1. Default constructor
A constructor which takes zero number of arguments is called a default constructor (we don’t need to pass any argument at the time of object creation).
- If we did not create a default constructor, then the c++ compiler automatically creates a default constructor.
Example
#include <iostream>
using namespace std;
class Student {
public:
string studentName;
int sAge;
// default constructor
Student() {
studentName = "";
sAge = 0;
}
void printInfo() {
cout << "Student name is : " << studentName << endl;
cout << "Student age is : " << sAge << endl;
}
};
int main(int argc, char const *argv[]) {
Student s1;
s1.studentName = "Online Vidyalay";
s1.sAge = 32;
// calling method
s1.printInfo();
return 0;
}
// output
// Student name is : Online Vidyalay
// Student age is : 322. Parameterized constructor
A constructor which takes at least one argument is called a parameterized constructor.
#include <iostream>
using namespace std;
class Student {
public:
string studentName;
int sAge;
// constructor
Student(string name, int age) {
studentName = name;
sAge = age;
}
void printInfo() {
cout << "Student name is : " << studentName << endl;
cout << "Student age is : " << sAge << endl;
}
};
int main(int argc, char const *argv[]) {
Student s1("Online Vidyalay", 32);
// calling method
s1.printInfo();
return 0;
}
// output
// Student name is : Online Vidyalay
// Student age is : 32
2. Copy constructor
It passes reference of an object as a parameter called copy constructor.
There are two ways to execute a copy constructor itself.
- shallow copy
- deep copy