有没有一组预处理器(ANSI C 89/ISO C 90兼容),它能在C中实现某种(但有用)的对象定向?
发布于 2018-03-23 14:47:12
为了简化和灵活起见,它尽量减少可用的概念:统一的面向对象编程,包括lasses, metaclasses, property metaclasses, generics, multimethods, delegation, ownership, exceptions, contracts 和 closures。
发布于 2018-03-23 15:36:55
您只需使用普通的结构作为对象,并通过指针传递它们:
struct monkey
{
float age;
bool is_male;
int happiness;
};
void monkey_dance(struct monkey *monkey)
{
/* do a little dance */
}
要获得诸如继承和多态性之类的东西,您必须更加努力地工作。您可以通过让结构的第一个成员成为超类的实例来进行手动继承,然后可以自由地转换到基类和派生类的指针:
struct base
{
/* base class members */
};
struct derived
{
struct base super;
/* derived class members */
};
struct derived d;
struct base *base_ptr = (struct base *)&d; // upcast
struct derived *derived_ptr = (struct derived *)base_ptr; // downcast
要获得多态性(即虚拟函数),您可以使用函数指针,也可以选择函数指针表,也称为虚拟表或vtable:
struct base;
struct base_vtable
{
void (*dance)(struct base *);
void (*jump)(struct base *, int how_high);
};
struct base
{
struct base_vtable *vtable;
/* base members */
};
void base_dance(struct base *b)
{
b->vtable->dance(b);
}
void base_jump(struct base *b, int how_high)
{
b->vtable->jump(b, how_high);
}
struct derived1
{
struct base super;
/* derived1 members */
};
void derived1_dance(struct derived1 *d)
{
/* implementation of derived1's dance function */
}
void derived1_jump(struct derived1 *d, int how_high)
{
/* implementation of derived 1's jump function */
}
/* global vtable for derived1 */
struct base_vtable derived1_vtable =
{
&derived1_dance, /* you might get a warning here about incompatible pointer types */
&derived1_jump /* you can ignore it, or perform a cast to get rid of it */
};
void derived1_init(struct derived1 *d)
{
d->super.vtable = &derived1_vtable;
/* init base members d->super.foo */
/* init derived1 members d->foo */
}
struct derived2
{
struct base super;
/* derived2 members */
};
void derived2_dance(struct derived2 *d)
{
/* implementation of derived2's dance function */
}
void derived2_jump(struct derived2 *d, int how_high)
{
/* implementation of derived2's jump function */
}
struct base_vtable derived2_vtable =
{
&derived2_dance,
&derived2_jump
};
void derived2_init(struct derived2 *d)
{
d->super.vtable = &derived2_vtable;
/* init base members d->super.foo */
/* init derived1 members d->foo */
}
int main(void)
{
/* OK! We're done with our declarations, now we can finally do some
polymorphism in C */
struct derived1 d1;
derived1_init(&d1);
struct derived2 d2;
derived2_init(&d2);
struct base *b1_ptr = (struct base *)&d1;
struct base *b2_ptr = (struct base *)&d2;
base_dance(b1_ptr); /* calls derived1_dance */
base_dance(b2_ptr); /* calls derived2_dance */
base_jump(b1_ptr, 42); /* calls derived1_jump */
base_jump(b2_ptr, 42); /* calls derived2_jump */
return 0;
}
https://stackoverflow.com/questions/-100003675
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