How to get the value of enum from a string - c

Question

code is here!
I tried to get the value of enum value as string from the user input and want to decode the value and print the case according to it, using Switch case but can't decode the exact value.
enum design {E2F = 1, E2, E3, E4, E5}; char *designation[5];
If someone helps I will be happy
Thanks.

Answer 1

An enum maps symbols to numbers. Here are the 3 options we discussed:
If you want to map strings to numbers use a struct:
struct {
const char *design;
int value;
} designs[] = {
{"E2F", 1},
{"E2", 2},
{"E3", 3}
{"E4", 4},
{"E5", 5}
};
If you want the struct defined in terms of the enum. Generate both from the same data (DESIGNS):
#define DESIGNS\
_(E2F, 1)\
_(E2, 2)\
_(E3, 3)\
_(E4, 4)\
_(E5, 5)
#define _(A, B) A = B,
enum {
DESIGNS
};
#undef _
#define _(A, B) { #A, A },
struct {
const char *design;
int value;
} designs[] = {
DESIGNS
};
which the pre-processor would expand to:
enum {
E2F = 1, E2 = 2, E3 = 3, E4 = 4, E5 = 5,
};
struct {
const char *design;
int value;
} designs[] = {
{ "E2F", E2F }, { "E2", E2 }, { "E3", E3 }, { "E4", E4 }, { "E5", E5 },
};
And here is #DavidCRankin's suggestion (if I understood it right) to just store the array to derive the value from the index:
#include <string.h>
int design_to_number(const char *str) {
const char *designs[] = { "E2F", "E2", "E3", "E4", "E5" };
for(int i = 0; i < sizeof(designs) / sizeof(*designs); i++) {
if(!strcmp(designs[i], str)) return i + 1;
}
return -1;
}

Answer 2

C enum values are just named integers. For string conversion, you'll need to roll our own (unlike Java, for example, where enums are more powerful). One way to go about conversion from string to enum is use the library bsearch function:
#include <stdlib.h>
#include <assert.h>
#include <string.h>
enum design {E2F = 1, E2, E3, E4, E5};
struct design_value {
const char *design;
enum design value;
} designs[] = {
{"E2", E2},
{"E2F", E2F},
{"E3", E3},
{"E4", E4},
{"E5", E5},
};
static int design_value_cmp(const void *a, const void *b) {
return strcmp(((struct design_value*) a)->design, ((struct design_value*) b)->design);
}
enum design get_design(char *designation) {
struct design_value key[1] = {{ designation }};
struct design_value *result = (struct design_value*) bsearch(
key,
designs, sizeof designs / sizeof designs[0], sizeof designs[0],
design_value_cmp);
assert(result);
return result->value;
}
// Tiny verifier. Don't use scanf("%s"...) in real code.
#include <stdio.h>
int main(void) {
char buf[100];
scanf("%s", buf);
printf("%d\n", get_design(buf));
return 0;
}
Note bsearch requires that the strings be in alpha order.