如何根据字符串的值访问`struct'的成员？

Question

I would like to access a member within a struct by using the value of a string:

struct hello_world
{
           char rate;
           char ssid;
};

There is a varibale let's say

char *string="ssid";

I would like to use the value of this string to refer to the ssid member within the hello_world struct. Is this possible?

Answer 1

Nope, it's not.

You need a (long) if-else statement, that will do this. Like:

struct hello_world hw;
char *string="ssid";

if( 0 == strcmp( "ssid", string ) )
{
     // use hw.ssid
}
else if ...

Answer 2

Instead of using a string, you are better off using an enum with all the possible cases.

typedef enum {
    FIELD_SSID,
    FIELD_RATE,
} field_t

field_t string;

and then use a switch

switch (string) {
    case FIELD_SSID:
        //use ssid
        break;
    case FIELD_RATE:
        //use rate
        break;
}

This method is way faster than comparing strings.

If you only use one field OR the other, you could use a union instead of a struct.

Answer 3

Define a function, like a wrapper to pass the member back you want.

char GiveMember(struct hello_world, char* member){ }

But the language itself does not provide you with anything like this.