Copy constructor vs assignment operator in C++

 

　　Difficulty Level: Rookie

　　Consider the following C++ program.

#include<iostream>
#include<stdio.h>

using namespace std;

class Test
{
public:
    Test() 
    {
    }
    Test(const Test &t)
    {
        cout<<"Copy constructor called "<<endl;
    }
    Test& operator = (const Test &t)    //仅仅为测试
    {
        cout<<"Assignment operator called "<<endl;
        return *this;
    }
};

int main()
{
    Test t1, t2;
    t2 = t1;
    Test t3 = t1;
    getchar();
    return 0;
}

　　Output:
　　Assignment operator called
　　Copy constructor called

 

　　Copy constructor is called when a new object is created from an existing object, as a copy of the existing object (see this G-Fact).

　　And assignment operator is called when an already initialized object is assigned a new value from another existing object.

　　t2 = t1;  // calls assignment operator, same as "t2.operator=(t1);"
　　Test t3 = t1;  // calls copy constructor, same as "Test t3(t1);"

 

 

　　References:http://en.wikipedia.org/wiki/Copy_constructor

 

 

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　　2013-11-26　　21:23:27