(C++) copy constructor

 

A copy constructor is the constructor called when an instance is copied.

 

A copy constructor is a constructor in which the first argument is a reference to an object that has the same type as the object to be initialized.

 

---

#include <cassert> #include <cstdlib> struct MyClass {   //MyClass construtor   MyClass(const int x = 0) : m_x(x) {}   //MyClass copy constructor   MyClass(const MyClass& other) : m_x(other.m_x) {}   //MyClass copy asignment constructor   MyClass& operator=(const MyClass& rhs)   {     //Identity test, advised by Scott Meyers. Effective C++ (3rd edition). Item 11.     if (this == &rhs) return *this;     const_cast<int&>(m_x) = rhs.m_x;     return *this;   }   //MyClass data member   const int m_x; }; int main() {   const int x = std::rand();   MyClass a(x) ;     //Call of constructor   MyClass b(a) ;     //Call of copy constructor   MyClass c = b;     //Converted to call of copy constructor   MyClass d = c = b; //Call of copy assignment operator   assert(a.m_x == b.m_x);   assert(a.m_x == c.m_x);   assert(a.m_x == d.m_x); }

 

 

 

 

 

References

 

1. Joint Strike Fighter Air Vehicle C++ Coding Standards for the System Development and Demonstration Program. Document Number 2RDU00001 Rev C. December 2005. 4.3.11: 'A copy constructor is a constructor in which the first argument is a reference to an object that has the same type as the object to be initialized.'