枚举结构的成员？ [英] Enumerate members of a structure?

问题描述

有没有一种方法来枚举结构的成员|在C（结构类）++或C？我需要得到成员名称，类型和值。我以前用过下面的示例code上的一个小项目，其中的变量是全局范围。我现在的问题是，一组值需要从GUI复制到一个对象，文件，以及VM环境。我可以创造另一个穷人的反射系统或希望更好的东西，我没有考虑过的。有没有人有什么想法？

编辑：我知道C ++不具有反射

 工会variant_t {
   unsigned int类型的用户界面;
   INT I;
   双D;
   字符* S;
};结构pub_values​​_t {
   为const char *名称;
   工会variant_t *地址;
   char类型; //'我'为int; 'U'是无符号整型; 'D'为双; 'S'是字符串
};＃定义pub_v（N，T）#N（工会variant_t *）及N，T
结构pub_values​​_t pub_values​​ [] = {
   pub_v（somemember，D），
   pub_v（somemember2，D），
   pub_v（somemember3，'U'），
   ...
};const int的no_of_pub_vs = sizeof的（pub_values​​）/的sizeof（结构pub_values​​_t）;
 

解决方案

不言自明的，有C或C无反射++。因此，（默认）列举的成员变量没有可靠的方法。

如果你有控制你的数据结构，你可以尝试的std ::矢量＆lt;提高::任何＆GT; 或的std ::地图＆LT;的std ::字符串，提振::任何＆GT; 那么你的所有成员变量添加到矢量/图。

当然，这意味着所有的变量很可能会在堆上所以会有一个性能命中本办法。随着性病::地图的方法，这意味着你将有一种穷人的反思。

Is there a way to enumerate the members of a structure (struct | class) in C++ or C? I need to get the member name, type, and value. I've used the following sample code before on a small project where the variables were globally scoped. The problem I have now is that a set of values need to be copied from the GUI to an object, file, and VM environment. I could create another "poor man’s" reflection system or hopefully something better that I haven't thought of yet. Does anyone have any thoughts?

EDIT: I know C++ doesn't have reflection.

union variant_t {
   unsigned int  ui;
   int           i;
   double        d;
   char*         s;
};

struct pub_values_t {
   const char*      name;
   union variant_t* addr;
   char             type;  // 'I' is int; 'U' is unsigned int; 'D' is double; 'S' is string
};

#define pub_v(n,t) #n,(union variant_t*)&n,t
struct pub_values_t pub_values[] = {
   pub_v(somemember,  'D'),
   pub_v(somemember2, 'D'),
   pub_v(somemember3, 'U'),
   ...
};

const int no_of_pub_vs = sizeof(pub_values) / sizeof(struct pub_values_t);

解决方案

To state the obvious, there is no reflection in C or C++. Hence no reliable way of enumerating member variables (by default).

If you have control over your data structure, you could try a std::vector<boost::any> or a std::map<std::string, boost::any> then add all your member variables to the vector/map.

Of course, this means all your variables will likely be on the heap so there will be a performance hit with this approach. With the std::map approach, it means that you would have a kind of "poor man's" reflection.

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