在创建复制构造函数时，为什么我们通过&

问题描述

Hi EveryBody，



任何人都可以在创建复制构造函数时解释为什么我们传递& ，为什么不重视任何人可以解释这个？





例如：

Hi EveryBody,

Can anyone can explain , while creating the copy constructor , why we are passing & ,why not value any one can explain about this?


Example:

#include <iostream>

using namespace std;

class Line
{
   public:
      int getLength( void );
      Line( int len );             // simple constructor
      Line( const Line &obj);  // copy constructor
      ~Line();                     // destructor

   private:
      int *ptr;
};

// Member functions definitions including constructor
Line::Line(int len)
{
    cout << "Normal constructor allocating ptr" << endl;
    // allocate memory for the pointer;
    ptr = new int;
    *ptr = len;
}

Line::Line(const Line &obj)
{
    cout << "Copy constructor allocating ptr." << endl;
    ptr = new int;
   *ptr = *obj.ptr; // copy the value
}

Line::~Line(void)
{
    cout << "Freeing memory!" << endl;
    delete ptr;
}
int Line::getLength( void )
{
    return *ptr;
}

void display(Line obj)
{
   cout << "Length of line : " << obj.getLength() << endl;
}

// Main function for the program
int main( )
{
   Line line(10);

   display(line);

   return 0;
}

问候，

Ranjith

Regards,
Ranjith

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