In C++, class variables are initialized in the same order as they appear in the class declaration.
Consider the below code.
1 #include<iostream>
2
3 using namespace std;
4
5 class Test
6 {
7 private:
8 int y;
9 int x;
10 public:
11 Test() : x(10), y(x + 10)
12 {
13 }
14 void print();
15 };
16
17 void Test::print()
18 {
19 cout<<"x = "<<x<<" y = "<<y;
20 }
21
22 int main()
23 {
24 Test t;
25 t.print();
26 getchar();
27 return 0;
28 }
The program prints correct value of x, but some garbage value for y, because y is initialized before x as it appears before in the class declaration.
So one of the following two versions can be used to avoid the problem in above code.
1 // First: Change the order of declaration.
2 class Test
3 {
4 private:
5 int x;
6 int y;
7 public:
8 Test() : x(10), y(x + 10)
9 {
10 }
11 void print();
12 };
13
14 // Second: Change the order of initialization.
15 class Test
16 {
17 private:
18 int y;
19 int x;
20 public:
21 Test() : x(y-10), y(20)
22 {
23 }
24 void print();
25 };
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
转载请注明：http://www.cnblogs.com/iloveyouforever/
2013-11-26 10:23:29