将变量名转换为 C++ 中的字符串
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converting a variable name to a string in C++
提问by Wawel100
I'd like to output some data to a file. For example assume I have two vectors of doubles:
我想将一些数据输出到文件中。例如假设我有两个双精度向量：
vector<double> data1(10);
vector<double> data2(10);
is there an easy way to output this to a file so that the first row contains the headings 'data1' and 'data2' followed by the actual contents. The function which outputs the data will be passed various different arrays so hardcoding the name of the heading is not possible - ideally I'd like to convert the variable name to some string and then output that string followed by the contents of the vector array. However, I'm not sure how to convert the variable name 'data1' to a string, or indeed if it can easily be done (from reading the forums my guess is it can't) If this is not possible an alternative might be to use an associative container such as map or perhaps more simply a 'pair' container.
有没有一种简单的方法可以将其输出到文件，以便第一行包含标题“data1”和“data2”，后跟实际内容。输出数据的函数将传递各种不同的数组，因此不可能对标题的名称进行硬编码 - 理想情况下，我想将变量名称转换为某个字符串，然后输出该字符串，后跟向量数组的内容。但是，我不确定如何将变量名 'data1' 转换为字符串，或者实际上是否可以轻松完成（从阅读论坛我的猜测是它不能）如果这是不可能的，另一种可能是使用关联容器，例如地图或更简单的“配对”容器。
pair<vector<double>,string> data1(10,'data1');
Any suggestions would be welcome!
欢迎大家提出意见！
回答by sarnold
You can use the preprocessor "stringify" #to do what you want:
您可以使用预处理器“stringify”#来执行您想要的操作：
#include <stdio.h>
#define PRINTER(name) printer(#name, (name))
void printer(char *name, int value) {
printf("name: %s\tvalue: %d\n", name, value);
}
int main (int argc, char* argv[]) {
int foo = 0;
int bar = 1;
PRINTER(foo);
PRINTER(bar);
return 0;
}
name: foo value: 0
name: bar value: 1
(Sorry for printf, I never got the hang of <iostream>. But this should be enough.)
（抱歉printf，我从来没有掌握<iostream>。但这应该足够了。）
回答by SaeidMo7
try this:
尝试这个：
#define GET_VARIABLE_NAME(Variable) (#Variable)
//in functions
//在函数中
int var=0;
char* var_name= GET_VARIABLE_NAME(var);
回答by Puppy
You can use the preprocessor, there's a stringify token, but it's only available from the source, not to a function (you'd get the argument name).
您可以使用预处理器，有一个 stringify 标记，但它只能从源中获得，不能从函数中获得（您将获得参数名称）。
回答by thiagowfx
Slightly adapted from @sarnold's answer, for C++:
稍微改编自@sarnold 的回答，适用于 C++：
#define DEBUG(x) std::cout << #x << " = " << x << std::endl;
An example program which uses this:
一个使用这个的示例程序：
int main() {
int foo = 1;
DEBUG(foo);
return 0;
}
回答by Timmy_A
I had the same problem. After a little bit of experimentation I created following macros that convert names of variables, fields, functions, methods and types to strings.
我有同样的问题。经过一些实验，我创建了以下宏，将变量、字段、函数、方法和类型的名称转换为字符串。
#define MACRO_VARIABLE_TO_STRING(Variable) (void(Variable),#Variable)
#define MACRO_FUNCTION_TO_STRING(Function) (void(&Function),#Function)
#define MACRO_METHOD_TO_STRING(ClassName,Method) (void(&ClassName::Method),#Method)
#define MACRO_TYPE_TO_STRING(Type) (void(sizeof(Type)),#Type)
The code uses comma operator and void conversion to force compiler to check if variable, function, etc. really exists. The nice thing is that it works well with uninitialized variables too. I tested it on both VC and GCC with all pedantic options I found out without any warning messages.
代码使用逗号运算符和void 转换来强制编译器检查变量、函数等是否真的存在。好消息是它也适用于未初始化的变量。我在 VC 和 GCC 上使用我发现的所有迂腐选项对其进行了测试，没有任何警告消息。
int GetAndPrintValue(const char* VariableName)
{
std::cout << VariableName << std::endl;
return 10;
}
int Variable=GetAndPrintValue(MACRO_VARIABLE_TO_STRING(Variable));
I use such code when I write parsers that reads data from input stream and if parsed variable is out of bounds it throws an exception with name of variable that failed my validity checks.
当我编写从输入流读取数据的解析器时，我使用这样的代码，如果解析的变量超出范围，它会抛出一个异常，其中变量的名称未通过我的有效性检查。
回答by Timmy_A
I'd have thought the obvious answer is to make the function that performs the output take the heading text as a string parameter.
我原以为显而易见的答案是让执行输出的函数将标题文本作为字符串参数。
回答by Dmitry Bravikov
For this case I have made nameof()macro. It returns a std::string name of a variable, type or member. It works like nameof() in C#.
对于这种情况，我制作了nameof()宏。它返回一个变量、类型或成员的 std::string 名称。它的工作原理类似于 C# 中的 nameof()。
For Example:
例如：
#include "nameof.h"
std::vector<double> data1(10);
std::string name = nameof(data1); // "data1"
struct Foo1
{
struct Foo2
{
Foo1* foo1;
};
Foo1* foo1;
Foo2 foo2;
};
name = nameof(Foo1::foo1->foo2.foo1); // "foo1"
name = nameof(123); // std::logic_error exception
