Emulate Swift enum types in C

swift-enum.c

#include <stdio.h>

/**
 * Emulate Swift enum type.
 */
typedef struct {
    // define enum types
    // (enums inside structs are not really private)
    enum {
        MyEnumInt,
        MyEnumString,
        MyEnumTuple,
    } type;
    // define field for each enum value
    union {
        int i;
        char* s;
        struct {
            int x;
            int y;
        }; // optionally define field name, e.g., "t";
    };
} MyEnum;

/**
 * Print enum value.
 */
static void printEnum(MyEnum const* myEnum) {
    switch (myEnum->type) {
        case MyEnumInt: {
            printf("type.a: %d\n", myEnum->i);
            break;
        }
        case MyEnumString: {
            printf("type.b: %s\n", myEnum->s);
            break;
        }
        case MyEnumTuple: {
            printf("type.x: %d, type.y: %d\n", myEnum->x, myEnum->y);
            break;
        }
    }
}

int main() {
    // define enum variable
    MyEnum myEnum;

    // set int type together with its corresponding value
    myEnum = (MyEnum) {
        .type = MyEnumInt,
        .i = 9,
    };

    printEnum(&myEnum);

    // set string type together with its corresponding value
    myEnum = (MyEnum) {
        .type = MyEnumString,
        .s = "string",
    };

    printEnum(&myEnum);

    // set tuple type together with its corresponding values
    myEnum = (MyEnum) {
        .type = MyEnumTuple,
        .x = 212,
        .y = -476,
    };

    printEnum(&myEnum);

    return 0;
}