c - 如何在 c 用户定义函数中返回 "struct"数据类型？

Question

我需要读取5个城市名称，我的代码有什么问题，请解释我不想使用 void 数据类型

//read the 5 city using struct
struct census
{
    char city[20];
    int popullation;
    float literacy;
};

struct census citi[5];
struct census read(struct census citi[]);

main()
{
   int i;
   citi= read(citi);
   for(i=0;i<5;i++)
   {
       printf("%s",citi[i].city);
       printf("\n");
   }
}

struct census read(struct census citi[])
{
    int i;
    for(i=0;i<5;i++)
        gets(citi[i].city);

    return(citi);
}

如何使用数据类型 struct 返回值，请发现错误并解释错误

Answer 1

您的程序不要求您从 read() 函数返回任何内容。不要调用自己的函数read()，因为那是标准函数的名字，所以这样定义会更好

void readCities(struct census *citi, size_t count)
{
    size_t index;
    for (index = 0 ; index < count ; index++)
     {
        fgets(citi[i].city, sizeof(citi[i].city), stdin);
     }
}

和 main()

#include <stdio.h>
#include <stdlib.h>

struct census
{
    char city[20];
    int popullation;
    float literacy;
};
void readCities(struct census *citi);

int main()
{
   size_t        index;
   struct census citi[5];

   readCities(citi, sizeof(citi) / sizeof(*citi));
   for (index = 0 ; index < 5 ; index++)
    {
       printf("%s\n", citi[index].city);
    }
   return 0;
}

上面的代码将初始化 struct，如您所见，您不需要全局变量，除非您真的知道自己在做什么，否则不要使用全局变量，如 @ Weather Vane在下面评论，你可以检查 fgets() 的返回值并返回成功读取结构的数量，而不是根本不返回，就像这样

#include <stdio.h>
#include <stdlib.h>

struct census
{
    char city[20];
    int popullation;
    float literacy;
};
size_t readCities(struct census *citi);

int main()
{
   size_t        index;
   struct census citi[5];
   size_t        count

   count = readCities(citi, sizeof(citi) / sizeof(*citi));
   for (index = 0 ; index < count ; index++)
    {
       printf("%s\n", citi[index].city);
    }
   return 0;
}

size_t readCities(struct census *citi, size_t count)
{
    size_t index;
    size_t successfulCount;

    successfulCount = 0;
    for (index = 0 ; index < count ; index++)
     {
        if (fgets(citi[i].city, sizeof(citi[i].city), stdin) != NULL)
            successfulCount += 1;
     }

    return successfulCount;
}