在创建C ++枚举和依赖数据结构时，如何避免重复？ [英] How can I avoid repeating myself when creating a C++ enum and a dependent data structure?

问题描述

可能重复：

枚举到字符串：如果无效/未找到则返回枚举整数值

简单来说，我的工作定义代码是这样的：

In brief, the (working) definition code that I have is something like this:

enum Gadget
{
    First,
    Second,
}; 

const char* gadget_debug_names[] = {
    "First",
    "Second",
    // note: strings are same as enum tokens here, but bonus points if
    //       they can optionally be given different values
};

但是，很容易出现信息在多个单独的地方，必须手动维护。 （在某些情况下，在代码库中，我正在使用这两个 - 或更多的地方甚至不在同一个文件中。）所以，只要命名这些东西，真的很好。

However, it's error prone that the information is in multiple separate places that have to be maintained manually. (And in some cases in the code base I'm working with those two--or more--places aren't even currently in the same file.) So it would be really nice to just name those things once.

现在我们可以使用代码生成和声明式数据文件来实现这一点，但是如果有更好的方法，我不想在现有的构建过程中添加另一个步骤。

Now we could do this with code generation and a declarative data file, but I'd prefer not to add another step to the existing build process if there's a better way to do this. It would be perfect to have something that looks like

DEFINE_GADGET(First)
DEFINE_GADGET(Second)

（如果需要，可选择使用start / stop宏）但是，由于宏只是纯文本替换，以任何方式让预处理器在写出枚举定义时记住令牌。

(optionally with start/stop macros if needed) But, since macros are just plain text substitution, I can't figure out any way to have the preprocessor "remember" the tokens while it's writing out the enum definition.

我认为这也可能是通过元编程，但我在如何做到亏损。我看到的所有例子涉及递归地建立一个数据结构。我可以看到我可以如何构建字符串数组的方式，但我不知道如何传递一个令牌名称，或如何构建一个枚举。 （当然使用元编程只是为了构建一个字符串数组将是很可笑的。）

I've thought that this might also be possible through meta-programming, but I'm at a loss on how to do it. All of the examples I've seen there involve recursively building a data structure. I can see how I might build the array of strings that way, but I'm not sure how I could pass in a token name, or how to build an enum. (And of course using metaprogramming just to build an array of strings would be pretty ridiculous.)

有没有办法让我在这里保持DRY，而不使用代码生成？

Is there any way for me to keep DRY here, without using code generation?

推荐答案

这里有一个旧的预处理技巧：

There is an old pre-processor trick for this:

DEFINE_GADGET(First)
DEFINE_GADGET(Second)

小工具。 * *

Gadget.**

#define QUOTE_VAL(X)  #X

enum Gadget
{
#define DEFINE_GADGET(X)   X,
#include "Gadget.data"
#undef DEFINE_GADGET(X)
}; 

const char* gadget_debug_names[] = {
#define DEFINE_GADGET(X)   QUOTE_VAL(X),
#include "Gadget.data"
#undef DEFINE_GADGET(X)
};

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