Question

我尝试使用虚函数表在C中使用虚函数实现集合，并且由于错误而导致初始化虚函数表时出现问题：

error: designator in initializer for scalar type 'set *' (aka 'struct _set *')

我被赋予了（它的任务）一个通用的＆＃39; set.c＆＃39;和＆＃39; set.h＆＃39;文件作为一个接口，所以我怀疑我可能没有接近正确实现它的想法。

以下是集合标题的相关部分：

typedef struct _set{
  const struct _set_vtable *vtable;
  const item_vtable *i_vtable;
  int size;
} set;

typedef bool (*SET_ADD_FXN)(set *, const void *);
typedef bool (*SET_CONTAINS_FXN)(const set *, const void *);
typedef void (*SET_PRINT_FXN)(const set *);
typedef void (*SET_DESTROY_FXN)(set *);

typedef struct _set_vtable
{
  SET_ADD_FXN add;
  SET_CONTAINS_FXN contains;
  SET_PRINT_FXN print;
  SET_DESTROY_FXN destroy;
} set_vtable;

bool set_add(set *s, const void *item);
bool set_contains(const set *s, const void *item);
void set_print(const set *s);
void set_destroy(set *s);
int set_size(const set *s);

set.c文件只是通过set函数表将函数调用转发给指向的函数：

bool set_add(set *s, const void *item)
{
  return s->vtable->add(s, item);
}
...

所以，这是我尝试实施＆＃39; set231＆＃39;这是一个具有特定功能的集合：

//set231.h
#include "set.h"

typedef struct{
  set * const interface;
  const char **items;
} set231;

set231 *set231_create();
int set231_size(set231 *);

bool set231_add(set231 *, const void *);
bool set231_contains(const set231 *, const void *);
void set231_print(const set231 *);
void set231_destroy(set231 *);

extern set_vtable set231_vtable;
extern item_vtable set231_ivtable;

//set231.c
#include "set231.h"

const int INITIAL_CAPACITY = 4;
const int STRING_LENGTH = 16;

set231 *set231_create(){
set231 *new = {
  .interface = &((set *){
    .vtable = &set231_vtable,
    .i_vtable = &((item_vtable *){
      .compare = strcmpv,
      .destroy = free,
      .print = str_print,
      .clone = strdupe
    }),
    .size = 0
  }),
  .items = (void *) malloc(sizeof(char *) * INITIAL_CAPACITY)
};
  return new;
}

int set231_size(set231 *s){...}

bool set231_add(set231 *s, const void *item){...}
bool set231_contains(const set231 *s, const void *item){...}
void set231_print(const set231 *s){...}
void set231_destroy(set231 *s){...}

set_vtable set231_vtable = 
{
  .add = set231_add,
  .contains = set231_contains,
  .print = set231_print,
  .destroy = set231_destroy
};
item_vtable set231_ivtable =
{
  .compare = strcmpv,
  .destroy = free,
  .print = str_print,
  .clone = strdupe
};

编译时，我得到初始化器错误的指示符，以及给出设置接口的虚拟表函数的警告，这些函数专门询问set231而不是set。

warning: incompatible pointer types initializing 'SET_ADD_FXN' (aka 'bool (*)(set *, const void *)') with an expression of type 'bool (set231 *, const void *)'

C错误：标量类型的初始化程序中的指示符＆＃39; item_vtable *＆＃39;

0 个答案: