Question

How to use function pointers inside a struct like OOP in C

Answer 1

// Struct With Multiple Function Pointers (“Methods”) (Object‑like Design)
 
#include <stdio.h>
 
typedef struct {
    void (*start)();
    void (*stop)();
} Motor;
 
void motorStart() { printf("Motor started\n"); }
void motorStop()  { printf("Motor stopped\n"); }
 
int main() {
    Motor m = { motorStart, motorStop };
 
    m.start();
    m.stop();
     
    return 0;
}
 
 
 
/*
run:
 
Motor started
Motor stopped
 
*/

 

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Answer 2

// Struct With Multiple Function Pointers
// “Methods” That Take the Struct Itself (OOP in C)

#include <stdio.h>

typedef struct Object {
    int x;

    void (*set)(struct Object*, int);
    void (*print)(struct Object*);
} Object;

void setX(Object* self, int v) {
    self->x = v;
}

void printX(Object* self) {
    printf("x = %d\n", self->x);
}

int main() {
    Object obj = { 10, setX, printX };
    
    obj.print(&obj);
    
    obj.set(&obj, 99);
    obj.print(&obj);

    return 0;
}


/*
run:

x = 10
x = 99

*/

 

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