cmake_demo/library/rect.c

#include "rect.h"

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

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

double _rect_area(void *self)
{
    struct _rect *pthis = (struct _rect *)self;
    double area = pthis->width * pthis->height;

    printf("rect area = %0.2f\n", area);
    return area;
}

void _rect_draw(void *self)
{
    printf("rect draw\n");
}

struct _rect *rect_new(double width, double height)
{
    // super
    static struct _virtual_table vtb = {
        .area = (double (*)(void *self))_rect_area,
        .draw = (void (*)(void *self))_rect_draw,
    };

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

    // self
    struct _rect *rect = calloc(1, sizeof(struct _rect));
    if (rect == NULL)
    {
        return NULL;
    }
    rect->me = rect;

    rect->width = width;
    rect->height = height;
    // set parent
    rect->shape = shape;

    return rect;
}