Copy constructor vs assignment operator in C++

　　Difficulty Level: Rookie

　　Consider the following C++ program.

 1 #include<iostream>
 2 #include<stdio.h>
 3
 4 using namespace std;
 5
 6 class Test
 7 {
 8 public:
 9     Test()
10     {
11     }
12     Test(const Test &t)
13     {
14         cout<<"Copy constructor called "<<endl;
15     }
16     Test& operator = (const Test &t)    //仅仅为测试
17     {
18         cout<<"Assignment operator called "<<endl;
19         return *this;
20     }
21 };
22
23 int main()
24 {
25     Test t1, t2;
26     t2 = t1;
27     Test t3 = t1;
28     getchar();
29     return 0;
30 }

　　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

　　Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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　　2013-11-26　　21:23:27