A **copy constructor** is a method of a class which initializes an object using another object of the *same* class. A copy constructor can be called in various scenarios. For example: 
* In the case where an object of a class is returned by value. 
* In the case of an object of a class being passed, by value, ​to a function as an argument.

A copy constructor can also be defined by a user; in this case, the default copy constructor is not called. 

> **Note:** A user-defined copy constructor is generally needed when an object owns pointers or non-shareable references to a file (for example).

# Syntax

A copy constructor has the following function declaration:

> **Note:** The object to a copy constructor is always passed by reference.

If the object is passed by value, then its copy constructor will be invoked and it would be stuck in an infinite recursion.

# Code

The following ​snippet illustrates an example of a copy constructor defined in the class `Coordinate`.

#include<iostream> 
using namespace std; 

class Coordinate 
{ 
  private: 
    int x_cor, y_cor; 

  public: 

    // default constructor
    Coordinate(int x, int y) 
    { 
      x_cor = x;
      y_cor = y;
    } 

	// Copy constructor 
	Coordinate(const Coordinate &cor) 
  {
    // Note how you can access the private attributes of
    // the object class in the copy constructor,
    x_cor = cor.x_cor;
    y_cor = cor.y_cor;
  } 

	int get_x_cor(){
    return x_cor; 
  }
  	

	int get_y_cor(){
    return y_cor; 
  }
}; 

int main() 
{ 
  // default constructor called here
	Coordinate cor1(2, 4); 

  // Copy constructor is called here 
	Coordinate cor2 = cor1; 
  // Another copy constructor is called here
  Coordinate cor3(cor1);

	// Showing results 
	cout << "cor1 = (" << cor1.get_x_cor() << "," << cor1.get_y_cor() << ")" << endl; 
	cout << "cor2 = (" << cor2.get_x_cor() << "," << cor2.get_y_cor() << ")" << endl; 
	cout << "cor3 = (" << cor3.get_x_cor() << "," << cor3.get_y_cor() << ")" << endl; 
	

	return 0; 
}


# Explanation
Let's take a closer look at the code:
- **Line 4**, we define a class named `Coordinate`.
- **Line 7**, we define `x_cor` and `y_cor` as `private` in class `Coordinate`.
- **Line 12-16**, we define the default constructor of class `Coordinate`.
- **Line 19-25**, we define the copy constructor and assigned values of  `cor`  objects to private members of `Coordinate` class (`x_cor` and `y_cor`.) 
- **Line 27-29 and 32-34**, we defined getter of `x_cor` and `y_cor` respectively.
- **Line 40**, we created object `cor1` with parameters (2,4).
 
- **Line 43**, we created another object `cor2` and copied values of `cor1` to `cor2` by using copy constructor.
- **Line 45**, we created object `cor3` and copied values of `cor1` using another method of copy constructor.
- **Line 48-50**, we print values of `cor1`, `cor2` and `cor3` respectively.


Copy constructor in C++

Syntax

Code

Explanation