常见的 C 问题我无法弄清楚 : request for member in something not a structure or union

Question

所以我制作了一个结构来保存有关客户的信息。我得到如上标题所述的编译器错误。我仍在学习指导，所以如果我说错了什么，请多多包涵。据我所知，我的 typedef 有一个指向 Client 实例的指针。这意味着我需要使用 -> 而不是 .对于客户的领域。但这也不管用，我会得到 dereferencing to incomplete type 的错误。任何指导或帮助都会很棒!

客户端.h

#ifndef CLIENT_H
#define CLIENT_H

typedef struct client_tag *Client;

#endif

客户端.c

#include "client.h"


struct client_tag {
    char id[5];
    char name[30];
    char email[30];
    char phoneNum[15];
};

以下文件从文件中读取客户端信息并将它们分配给变量:

#include "client.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main() {
    Client client1 = malloc(sizeof(Client));
    FILE *fp;
    ListType clientList;

    fp = fopen("clients.txt", "r");

    int lineSize = 200;
    char* line = malloc(lineSize);
    char* line2 = malloc(lineSize);
    char* line3 = malloc(lineSize);
    char* line4 = malloc(lineSize); 


    while (fgets(line, lineSize, fp) != NULL) { 
        strcpy(client1.id, line);
        strcpy(client1.name, fgets(line2, lineSize, fp));
        strcpy(client1.email, fgets(line3, lineSize, fp));
        strcpy(client1.phoneNum, fgets(line4, lineSize, fp));

        push(clientList, (void*)&client1);

        printf("ID: %s", line);
        printf("Name: %s", line2);
        printf("Email: %s", line3);
        printf("Phone Number: %s\n", line4);

        free(line);
        free(line2);
        free(line3);
        free(line4);

        line = malloc(lineSize);
        line2 = malloc(lineSize);
        line3 = malloc(lineSize);
        line4 = malloc(lineSize);

    }

}

这是我得到的错误:

    clientDriver.c: In function ‘main’:
clientDriver.c:23:17: error: request for member ‘id’ in something not a structure or union
   strcpy(client1.id, line);
                ^
clientDriver.c:24:17: error: request for member ‘name’ in something not a structure or union
   strcpy(client1.name, fgets(line2, lineSize, fp));
                ^
clientDriver.c:25:17: error: request for member ‘email’ in something not a structure or union
   strcpy(client1.email, fgets(line3, lineSize, fp));
                ^
clientDriver.c:26:17: error: request for member ‘phoneNum’ in something not a structure or union
   strcpy(client1.phoneNum, fgets(line4, lineSize, fp));

Answer 1

我认为问题在于，如果您的头文件中没有 client_tag 的声明，则您不能在 client_tag * 或 client_tag 上使用字段。

我的建议是将 client_tag 的结构声明从 client.c 移动到 client.h

根据上述说明，编译运行如下代码

客户端.h

#ifndef CLIENT_H
#define CLIENT_H

struct client_tag {
    char id[5];
    char name[30];
    char email[30];
    char phoneNum[15];
};

typedef struct client_tag *Client;

#endif

主.c

#include "client.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

/* Minimal list implementation
 * Based on functions in your program
 */
typedef struct {
  unsigned length;
  size_t allocated_size;
  void ** items; 
} ListType;

/* Push implemented based on the usage in your code */
int push(ListType l, void* item){
  // check if we need to allocate memory
  if (l.length >= l.allocated_size){
    size_t next_size = (l.allocated_size > 0) ? l.allocated_size * 2 : sizeof(void*);
    l.items = (void **) realloc(l.items, next_size);
    if (l.items == NULL){
      return -1; // error
    }

    l.allocated_size = next_size;
  }

  // push the item;
  l.items[l.length++] = item;
  return l.length;
}

int main() {
    Client client1 = malloc(sizeof(Client));
    FILE *fp;
    ListType clientList;

    fp = fopen("clients.txt", "r");

    int lineSize = 200;
    char* line = malloc(lineSize);
    char* line2 = malloc(lineSize);
    char* line3 = malloc(lineSize);
    char* line4 = malloc(lineSize); 


    while (fgets(line, lineSize, fp) != NULL) { 
        strcpy(client1->id, line);
        strcpy(client1->name, fgets(line2, lineSize, fp));
        strcpy(client1->email, fgets(line3, lineSize, fp));
        strcpy(client1->phoneNum, fgets(line4, lineSize, fp));

        push(clientList, (void*)&client1);

        printf("ID: %s", line);
        printf("Name: %s", line2);
        printf("Email: %s", line3);
        printf("Phone Number: %s\n", line4);

        free(line);
        free(line2);
        free(line3);
        free(line4);

        line = malloc(lineSize);
        line2 = malloc(lineSize);
        line3 = malloc(lineSize);
        line4 = malloc(lineSize);

    }

}

客户端.txt

1
John Doe
john.doe@example.com
1-555-456-7890