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
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2013-11-26 21:23:27