Parameterized constructor in C++
What is parameterized constructor ?
Let us learn about parameterized constructor in C++ more, in this article. In C++, there are three types of constructor namely default constructor, parameterized constructor and copy constructor.
Definition
A constructor is a special member function whose task is to initialize the objects of its class. It is special because its name is same as the class name. The constructor is invoked whenever an object of its associated class is created. A constructor constructs the values of data members of the class hence it is called as constructor.
Benefits of parameterized constructor
- Parameterized constructor helps in initializing each data member of the class to different values.
- Parameterized constructor is helpful for constructor overloading.
Parameterized Constructor (Inside Class)
Syntax
class class_name
{
public: class_name(variables) //Parameterized constructor declared
{
// initialization of variables
}
}; Example Code
#include
using namespace std;
class PrepInsta
{
private:
string name;
int age;
public:
PrepInsta(string val1, int val2)// Parameterized Constructor
{
name = val1;
age = val2;
}
string getName(){
return name;
}
int getAge(){
return age;
}
};
int main()
{
// Paramterized Constructor called
PrepInsta obj("John Snow", 25);
cout << "Name: " << obj.getName() << "\nAge: " << obj.getAge();
return 0;
}Output
Name: John Snow Age: 25
Parameterized Constructor (Outside Class)
Code
#include<iostream>
using namespace std;
class PrepInsta
{
private:
string name;
int age;
public:
// Parameterized Constructor declaration
PrepInsta(string name, int age);
string getName(){
return name;
}
int getAge(){
return age;
}
};
// declaration outside class
PrepInsta::PrepInsta(string val1, int val2)// Parameterized Constructor
{
name = val1;
age = val2;
}
int main()
{
// Paramterized Constructor called
PrepInsta obj("John Snow", 25);
cout << "Name: " << obj.getName() << "\nAge: " << obj.getAge();
return 0;
}Output
Name: John Snow
Age: 25
Syntax
class class_name
{
//declaration
class_name(variables);
};
class_name :: class_name(variables) //Parameterized constructor definition
{
// initialization of variables
} More Examples for Parameterized Constructor
Example 1
#include <iostream>
using namespace std;
class myClass {
private:
int a, b;
public:
// parameterized constructor
myClass (int a1, int b1){
a = a1;
b = b1;
}
int getA (){
return a;
}
int getB (){
return b;
}
};
int main ()
{
myClass obj1(10, 15);
cout << "obj1.a = " << obj1.getA() << endl;
cout << "obj1.b = " << obj1.getB() << endl;
return 0;
}
Output
obj1.a = 10 obj1.b = 15
Example 2
#include<iostream>
using namespace std;
class Student {
public:
int roll_no;
string st_name;
float weight;
Student (int num, string name, float w){
roll_no = num;
st_name = name;
weight = w;
}
void display (){
cout << roll_no << " " << st_name << " " << weight << endl;
}
};
int main(void) {
Student s1 = Student(1, "Karen", 91.1);
Student s2 = Student(2, "Phils", 67);
s1.display();
s2.display();
return 0;
}Output
1 Karen 91.1 2 Phils 67
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