Initialization of data members

　　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

巴特西

Initialization of data members

最新文章

热门文章