c++ anonymous union,struct -- 匿名联合体和机构体

c++ anonymous union,struct -- 匿名联合体和机构体

结构体和联合体各自的基本用法不赘述，仅说一下他们匿名时访问的情况。如果是token不同，可以直接跨层访问。例子

1. #include <iostream>
2. using namespace std;
3. struct zoo_obj{
4. string name;
5. union {
6. unsigned int property;
7. struct{ //plant
8. unsigned int
9. hasLeaf:1,
10. hasFlower:1,
11. hasTrunk:1,
12. hasRattan:1;
13. };
14. struct { //animal
15. unsigned int
16. isBackbone:1,
17. isOvipara:1,
18. hasLags:1,
19. hasWing:1;
20. };
21. };
22. };
23. int main(void)
24. {
25. zoo_obj peony = {"peony",0};
26. zoo_obj dog = {name:"dog",0};
27. dog.hasLags = true;
28. /* zoo_obj dog = {name:"dog",property:0};
29. * sorry, unimplemented: non-trivial designated initializers
30. * not supported
31. */
32. cout << peony.name << " hasLeaf " << peony.hasLeaf << endl;
33. cout << dog.name << " hasLags " << dog.hasLags << endl;
34. }

输出

1. peony hasLeaf 0
2. dog hasLags 1

不支持像列子中name样的指定访问。如果指定了会报错

1. sorry, unimplemented: non-trivial designated initializers not supported