数组元素的类型不完整

So basically i'm supposed to make a program that acts as a password manager for 5 different "websites". When I declare the functions and main method all in one file it runs perfectly. However when I use a header file I get the error shown

所以基本上我应该制作一个程序，作为5个不同“网站”的密码管理器。当我在一个文件中声明函数和main方法时，它运行得很完美。但是，当我使用头文件时，我收到错误

functions.h

#ifndef FUNCTIONS_H_  
#define FUNCTIONS_H_

struct entry;

void requestEntry(struct entry *data);
void displaySummary(struct entry *data);
void displayEntry(struct entry *data);

#endif

functions.c

#include <stdio.h>
#include "functions.h"

struct entry{
    char webName[32];
    char userName[32];
    char password[32];
};

void requestEntry(struct entry *data){
    printf("Please enter the following items: \n");
    printf("Website name: ");
    scanf("%s", data->webName);
    printf("Username: ");
    scanf("%s", data->userName);
    printf("Password: ");
    scanf("%s", data->password);
}

void displaySummary(struct entry *data){
    printf(" - %s\n", data->webName);
}

void displayEntry(struct entry *data){
    printf("Website: %s\n", data->webName);
    printf("Username: %s\n", data->userName);
    printf("Password: %s\n", data->password);

}

main.c

main.c中

#include <stdio.h>
#include <stdbool.h>
#include "functions.h"

int main()
{
struct entry sites[5];

for (int i = 0; i < 5; i++){
    requestEntry(&sites[i]);
}

printf("\n");
printf("Summary: \n");

for (int i = 0; i < 5; i++){
    printf("%d", (i + 1));
    displaySummary(&sites[i]);
}

bool cont = true;
int i;

while (cont){
    printf("Type in a number from 1 to 5 to pull up the entry, or type 0 to exit: ");
    scanf("%d", &i);
    if (i == 0){
        cont = false;
        continue;
    }
    printf("\n");
    displayEntry(&sites[i - 1]);
}
}

ERROR: elements of array 'entry sites [5]' have incomplete type

错误：数组'入口站点[5]'的元素具有不完整的类型

I tried building the program in a different IDE and it said that my array size was too large, when its obviously only 5 structs. I know that the code I have does work because like I said it runs perfectly when everything is in one file.

我尝试在不同的IDE中构建程序，它说我的数组大小太大，显然只有5个结构。我知道我所拥有的代码确实有效，因为就像我说的那样，当一切都在一个文件中时，它运行得很好。

2 个解决方案

#1

The problem with such separation is that the inner structure of your struct entry becomes private to the functions.c translation unit. This may or may not be desirable.

这种分离的问题在于，struct entry的内部结构对于functions.c转换单元是私有的。这可能是也可能不是所希望的。

If you wish to keep the struct private, switch to dynamic allocation
如果您希望保持结构私有，请切换到动态分配
If you do not mind exposing your struct, move its definition to the header file.
如果您不介意公开结构，请将其定义移动到头文件中。

Here is the first approach: add a function to the header

这是第一种方法：向标题添加一个函数

struct entry *allocateEntries(size_t count);

Define this function in your functions.c file by calling malloc(sizeof(struct entry)*count). Now you can replace

通过调用malloc（sizeof（struct entry）* count）在functions.c文件中定义此函数。现在你可以替换

struct entry sites[5];

with

同

struct entry *sites = allocateEntries(5);

Don't forget to add free(sites) to the end of main().

不要忘记在main（）的末尾添加免费（站点）。

#2

You can't declare an array of struct entry somewhere where the definition of struct entry isn't visible; the compiler doesn't know how big to make each element of the array.

你不能在结构条目的定义不可见的地方声明一个struct entry数组;编译器不知道制作数组的每个元素有多大。

The straightforward thing, in your case, is to move the definition of struct entry from functions.c to functions.h.

在您的情况下，直接的事情是将struct entry的定义从functions.c移动到functions.h。

#1