cmake_demo/library/circle.c

#include "circle.h"

double circle_area(void *self)
{
    double area = 0;
    struct _circle *pthis = container_of(self, struct _circle, me);
    area = pthis->shape->vtb.area(pthis);
    return area;
}

void circle_draw(void *self)
{
    struct _circle *pthis = container_of(self, struct _circle, me);
    pthis->shape->vtb.draw(pthis);
}

double _circle_area(void *self)
{
    struct _circle *pthis = (struct _circle *)self;
    double area = 3.14 * pthis->radius * pthis->radius;
    printf("circle area = %0.2f\n", area);
    return area;
}

void _circle_draw(void *self,  void *parent)
{
    printf("circle draw\n");
}

struct _circle *circle_new(double radius)
{
    // super
    static struct _virtual_table vtb = {
        .area = (double (*)(void *self))_circle_area,
        .draw = (void (*)(void *self))_circle_draw,
    };

    struct _shape *shape = shape_new();
    if (shape == NULL)
    {
        return NULL;
    }
    shape->vtb = vtb;

    // self
    struct _circle *circle = calloc(1, sizeof(struct _circle));
    if (circle == NULL)
    {
        return NULL;
    }
    circle->me = circle;
    circle->radius = radius;
    // set parent
    circle->shape = shape;

    return circle;
}