Converting a Variable Name to a String in C++

C - Convert string to variable name

This is simply not possible in C.

Check out this question for more details.
How to return a variable name and assign the value of the variable returned in c

To quote Wichert, 'I suggest that you reconsider the problem you are trying to solve and check if there might not be a better method to approach it. Perhaps using an array, map or hash table might be an alternative approach that works for you.'

Convert any variable to string in C

I think the code below will do your work. I uses the standard sprintf function, which prints data from any type to a string, instead to stdout. Code:

#include <stdio.h>

#define INT_FORMAT "%d"
#define FLOAT_FORMAT "%f"
#define DOUBLE_FORMAT "%lf"
#define LL_FORMAT "%lld"
// ect ...

#define CONVERT_TO_STRING(FORMAT, VARIABLE, LOCATION) \
  do { \
    sprintf(LOCATION, FORMAT, VARIABLE); \
  } while(false)

int main() {
  char from_int[30];
  char from_float[30];
  char from_double[30];
  char from_ll[30];

  CONVERT_TO_STRING(INT_FORMAT, 34, from_int);
  CONVERT_TO_STRING(FLOAT_FORMAT, 34.234, from_float);
  CONVERT_TO_STRING(DOUBLE_FORMAT, 3.14159265, from_double);
  CONVERT_TO_STRING(LL_FORMAT, 9093042143018LL, from_ll);

  puts(from_int);
  puts(from_float);
  puts(from_double);
  puts(from_ll);

  return 0;
}

converting a variable name to a string in C++

You can use the preprocessor "stringify" # to do what you want:

#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.)

Programmatic way to get variable name in C?

You could try something like this:

#define DUMP(varname) fprintf(stderr, "%s = %x", #varname, varname);

I used to use this header I wrote, when I was new to C, it might contain some useful ideas. For example this would allow you to print a C value and provide the format specifier in one (as well as some additional information):

#define TRACE(fmt, var) \
        (error_at_line(0, 0, __FILE__, __LINE__, "%s : " fmt, #var, var))

If you're using C++, you could use the type of the passed value and output it appropriately. I can provide a much more lucrative example for how to "pretty print" variable values if this is the case.

Convert variable name to string

I managed to solve my problem with this code snippet:

Import the objc runtime

#import <objc/runtime.h>

and you can enumerate the properties with:

- (NSArray *)allProperties
{
    unsigned count;
    objc_property_t *properties = class_copyPropertyList([self class], &count);

    NSMutableArray *rv = [NSMutableArray array];

    unsigned i;
    for (i = 0; i < count; i++)
    {
        objc_property_t property = properties[i];
        NSString *name = [NSString stringWithUTF8String:property_getName(property)];
        [rv addObject:name];
    }

    free(properties);

    return rv;
}

Hope it helps someone.

Convert member variable name to a string

As others have said, the name of a variable doesn't actually exist in the generated code once the compiler has finished compiling the code. It may exist in debug symbols or some such, but that's a horrible mess to try to reach into to determine where your variable is located [it may well reside in different places depending on whether the compiler currently is using a register or memory location to store its value, etc, etc].

It is certainly possible to have a macro that produces the matching strin to a name in a parameter.

However, it's probably better to use a different mechanism for configuration type things - a couple of obvious options are:

1. Using a std::map<std::string, std::string>
2. Using an array or a vector of std::pair<std::string, std::string>

You could also have a piece of fixed code that understands different configuration settings and their translation to variables. It's not at all a bad solution as long as there aren't a huge number of them.

Or you could build an array like this:

enum config_vals
{
    host,
    color,
    ...
    max_config
};

struct translation
{
   const char *name;
   config_vals val;
};

#define TRANS(x) { #x, x }

translation trans[]] = {
    TRANS(host),
    TRANS(color),
};

class configitems
{
  ...
  std::string value[max_configs];
  ...
}

... 

configitems c;
...
if (c.value[host] == "localhost") ... 

Convert string to variable name or variable type

No, this is not possible. This sort of functionality is common in scripting languages like Ruby and Python, but C++ works very differently from those. In C++ we try to do as much of the program's work as we can at compile time. Sometimes we can do things at runtime, and even then good C++ programmers will find a way to do the work as early as compile time.

If you know you're going to create a variable then create it right away:

int count;

What you might not know ahead of time is the variable's value, so you can defer that for runtime:

std::cin >> count;

If you know you're going to need a collection of variables but not precisely how many of them then create a map or a vector:

std::vector<int> counts;

Remember that the name of a variable is nothing but a name — a way for you to refer to the variable later. In C++ it is not possible nor useful to postpone assigning the name of the variable at runtime. All that would do is make your code more complicated and your program slower.

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