Copy Constructor in C++

Updated March 16, 2023

Introduction to Copy Constructor in C++

 The programming languages provide us various features that can be leveraged to develop the application. In the case of middle-level languages, the features may be less compared to high-level languages but whatever options they offer are ample to develop significant applications. In this section, we will be learning about copy Constructors. The constructor may be defined as the special function that has the name as same as that of the class in which has been defined. The constructor is called automatically when the object of that class is initialized. It could be said that initializing the object if the class implicitly calls the constructor. If the constructor is overload than in that case the values have to be passed together with the object while initializing it. Here the type of constructor we will be learning is very unique and known as copy Constructor. This constructor works using other objects rather than normal values.

How does Copy Constructor work in C++?

Copy Constructor can be defined as the special type of constructor that is used to declare the object and initialize the same using other objects. The normal constructor called when the object of that class is initialized. If the constructor is overloaded with several parameters than initializing the object and passing the same number of arguments will call the overload parameter. As copy constructor is the overloaded one so it could be called when the object is initialized using the argument and the argument has to pass object value rather than any normal value.

Once the value received by the parameter of the overloaded constructor is found an object, the copy constructor will be called and the set of statements defined within the copy constructor will start executing. Before using copy constructor we have to create an object of the same class. It clearly states the approach that any program that is intended to implement copy constructor should also have a default or parameterized constructor so that the object could be created which will help in involving the copy constructor.

The overall scenario can be considered as leveraging one object in order to create another object. All the values bonded with the object that is used to initialize the object by copy constructor gets allocated to the newly initialized object. That means if the value of any variable is used by the first object, the same variable can be used by the object that is initialized by the copy constructor. The feature of copy constructor is considered very important and makes development very convenient for some applications. Its features to use the object reference of the same class helps in developing the application that has the requirement which can be fulfilled using the copy constructor only. Though it is not leveraged as often as the default or parameterized constructor, it is ample power to contribute to adding new functionality to the application.

Example of Copy Constructor in C++

Let’s understand the concept of copy constructor using the example. Here we will be working on a simple example that will show you how the copy constructor works and how it can access the values which were bound to the object using which the new object is created by the copy constructor. The below illustration will give you an idea about how it is different to call the copy constructor as compared to calling the normal overloaded constructor.

Code:

#include <iostream>
using namespace std;
class Check
{
public:
int val;
Check(int a)
{
val=a;
}
Check(Check &i)
{
val = i.val;
}
};
int main()
{
int add_val;
Check a1(50);
Check a2(a1);
add_val = a2.val + 10;
cout<<add_val;
}

In this program, we have called the parameterized constructor bypassing the argument through a1. The value passed is an integer as the parameterized constructor has been defined to accept integer only. When the value 50 is passed to the constructor, the value has been assigned to the variable named var. Then the object a1 has been passed to the copy constructor through a2. Once the object reference is received by the copy constructor, it bound the value allocated with the first object with the newly formed object. This is a simple example to explain the concept of the copy constructor. It could be used in several other programs to get various functionalities in the application.

Output:

Rules and Regulation for Copy Constructor in C++

Copy Constructor is considered a bit different from the default or parameterized constructor. On one hand, where the normal constructor works using the value of common datatype, on the other hand, copy constructor works using the previously created object of the same class. The thing that has to be ensured while using copy constructor is, the parameters passed through the copy constructor should be used together with an ampersand(&) sign as it is a special character that is used to hold the object reference. If ampersand is not used while implementing the copy constructor, it will no longer be a copy constructor but will be automatically considered as a parameterized constructor.

When it comes to calling the copy constructor, we have to make sure that the value passed as arguments should carry the object reference rather than any value that belongs to common datatype. These are the few things that have to be considered very sharply while implementing copy constructor in the C++ programming language. Also, every time we use the copy constructor we have to make sure that we are differentiating it properly from the parameterized constructor as failing this will totally change the functionality of the program and will lead to incorrect output generation.

Conclusion

The copy constructor is considered as a special kind of constructor that works using the object reference of the same class. It is used to bring several functionalities in the application. If compared with the default constructor, the copy constructor is not used very often in the simple programs but when it comes to developing complex applications that have to be deployed in the production environment, the copy constructor is used there and also makes application development pretty convenient.

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