动态地为结构变量赋值 [英] Dynamically assigning value to structure variable

问题描述

我试图动态地将值从文件中的结构中的变量，但不能弄清楚如何做。我有一个结构：

  struct abc {
 int age = 0; 
 string name =whatever; 
} * ABC; 
  

我还有一个函数循环通过一个文件，可以读取这些值，一个包含变量名称及其需要更新的值的行。例如，我可能会得到两个变量，如：

  KEY =age
 VAL = 21
  

之后，会出现以下文件的第一行：

  age | 21 
 name | bill 
  

如何将VAL值赋给ABC结构变量KEY？

谢谢！

UPDATE：

所以我想做类似的工作：

  ABC.KEY = VAL 
  

意义

  ABC.age = 21 
  

解决方案<

如果你想将键匹配到结构的成员

例如，您可以考虑这样：

  std :: unordered_map< std :: string，std :: function< void（std :: string，abc&）>映射; 
 mapping [age] = []（std :: string str，abc& a）{a.age = std :: stoi（str）; }; 
 mapping [name] = []（std :: string str，abc& a）{a.name = str; } 
  

现在您可以使用

这样的地图

  abc输出; 
 auto key = ... 
 auto value = ...; 
 if（mapping.find（key）== mapping.end（））
 throw ...; 
 mapping [key]（value，output）; 
  

I am trying to dynamically assign values from a file to variables in a structure, but can't figure out how to do it. I have a structure:

struct abc {
 int age = 0;
 string name = "whatever";
} *ABC;

I also have a function that loops through a file that can read these values so I would end up with a line that contains the variable name and its value that would need to be updated. So, for example, I might end up with two variables like:

KEY="age"
VAL="21"

after it processes the first line of the following file:

age|21
name|bill

How would I assign the VAL value to the ABC struct variable KEY?

Thanks!

UPDATE:

So I'm looking to do something like:

ABC.KEY = VAL

meaning

ABC.age = 21

解决方案

What you're looking for is known as reflection, and C++ does not offer this capability.

If you want to match keys to members of the struct, you will have to build a structure and functions to do so yourself.

For example, you may consider this:

std::unordered_map<std::string, std::function<void(std::string, abc&)>> mapping;
mapping["age"] = [](std::string str, abc& a) { a.age = std::stoi(str); };
mapping["name"] = [](std::string str, abc& a) { a.name = str; }

Now you can use the map like

abc output;
auto key = ...;
auto value = ...;
if (mapping.find(key) == mapping.end())
    throw ...;
mapping[key](value, output);

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