c - C中的结构(将值分配给结构数组)

Question

我有两个用 C 编写的不同代码。它们都只是尝试将值分配给结构。我正在使用 cs50 库来帮助我以简单的方式获取字符串。

对于第一个代码，当我尝试执行它时出现错误。

第一个代码:

#include <cs50.h>
#include <stdio.h>
#include <string.h>

#define MaxStudents 5

typedef struct
{
    string name;
    int age;
    string gender;
}
student;

student students[MaxStudents];

int main(void)
{
    students[0] = {"Kevin Mahendra", 22, "Male"};
    students[1] = {"Wasis Sirutama", 22, "Male"};
    students[2] = {"Alief Dean", 22, "Male"};
    students[3] = {"Adwi Lanang", 21, "Male"};
    students[4] = {"Dhimas Kuncahyo", 22, "Male"};

    for (int i = 0; i < MaxStudents; i++)
    {
        printf("%s, %i %s", students[i].name, students[i].age, students[i].gender);
    }

}

问题(第一个代码):

sorting.c:19:19: error: expected expression
    students[0] = {"Kevin Mahendra", 22, "Male"};
                  ^
sorting.c:20:19: error: expected expression
    students[1] = {"Wasis Sirutama", 22, "Male"};
                  ^
sorting.c:21:19: error: expected expression
    students[2] = {"Alief Dean", 22, "Male"};
                  ^
sorting.c:22:19: error: expected expression
    students[3] = {"Adwi Lanang", 21, "Male"};
                  ^
sorting.c:23:19: error: expected expression
    students[4] = {"Dhimas Kuncahyo", 22, "Male"};

但是对于第二个代码，它运行良好，没有任何错误。

第二个代码:

#include <cs50.h>
#include <stdio.h>
#include <string.h>

#define MaxStudents 5

struct student
{
    string firstName;
    string lastName;
    int age;
};

int main(void)
{
    struct student kevin = {"Kevin", "Mahendra", 22};
    
    printf("%s %s, %i\n", kevin.firstName, kevin.lastName, kevin.age);
}

那么你们认为我的第一个代码有什么问题？预期的表达方式是什么？

如您所见，我只是尝试将值赋值到结构数组中，就像我在第二个代码中所做的那样(但不是数组)。请帮我。谢谢。

Answer 1

初始化(第二段代码)和赋值(第一段代码)是有区别的

此语法仅在您初始化对象时有效，而不是在您赋值时有效。由于结构在分配时被复制，您可以为此使用复合文字:

#include <cs50.h>
#include <stdio.h>
#include <string.h>

#define MaxStudents 5

typedef struct
{
    string name;
    int age;
    string gender;
}
student;

student students[MaxStudents];

int main(void)
{
    students[0] = (student){"Kevin Mahendra", 22, "Male"};
    students[1] = (student){"Wasis Sirutama", 22, "Male"};
    students[2] = (student){"Alief Dean", 22, "Male"};
    students[3] = (student){"Adwi Lanang", 21, "Male"};
    students[4] = (student){"Dhimas Kuncahyo", 22, "Male"};

    for (int i = 0; i < MaxStudents; i++)
    {
        printf("%s, %i %s\n", students[i].name, students[i].age, students[i].gender);
    }
}

https://godbolt.org/z/KvE7G1