将变量从全局更改为局部-C [英] Changing a variable from global to local - C

问题描述

我已经为一个项目编写了以下代码，但是它未通过单个测试，要求两个变量不是全局变量，而是在main()中是局部变量.修改structexample1.c，以使变量student和anotherStudent不是全局变量，而是局部变量.我含糊地理解了本地和全球概念，但是我不确定如何在我编写的代码中实现问题所在.

I have written the following code for a project however it fails a singular test asking for two variables to not be global, and instead be local to main(). Modify structexample1.c so that the variables student and anotherStudent are not global but are local to main. I vaguely understand the local and global concept but I am unsure how to implement what the question is asking into the code I have written.

#include <stdio.h>
#include <stdlib.h>
struct student_s {
    char* name;
    int age;
    double height;
    struct student_s* next;   
} student;

struct student_s anotherStudent;

void printOneStudent(struct student_s student)
{
    printf("%s (%d) %s %s %.2lf %s\n", student.name, student.age, ",", "height", student.height, " m");
}   

void printStudents(const struct student_s* student)
{
    while (student != NULL) {
        printOneStudent(*student);
        student = student->next;
    }
}

int main(void)
{
    student.name = "Agnes McGurkinshaw";
    student.age = 97;
    student.height = 1.64;
    student.next = &anotherStudent;

    anotherStudent.name = "Jingwu Xiao";
    anotherStudent.age = 21;
    anotherStudent.height = 1.83;
    anotherStudent.next = NULL;

    printStudents(&student);
    return EXIT_SUCCESS;
}

我知道我需要在main()中定义这些变量，但是我不确定如何以不完全破坏我的代码的方式来实现它们.代码的输出应保持如下:

I know I will need to define these variables inside main() but I am unsure how to implement them in a way that does not entirely break my code. The output of the code should remain as follows:

Agnes McGurkinshaw (97), height 1.64 m
Jingwu Xiao (21), height 1.83 m

推荐答案

好吧，首先替换为:

struct student_s {
    char* name;
    int age;
    double height;
    struct student_s* next;   
} student;

使用:

struct student_s {
    char* name;
    int age;
    double height;
    struct student_s* next;   
};

(也就是说，删除最后一行中的student).

(That is, remove student in the last line).

此更改是必需的，因为您想要定义结构类型，以便以后可以定义类型为struct student_s的变量，但是您不想在此处定义student变量，因为那样会使它成为全局变量.

This change is necessary because you want to define the structure type so that you can later define variables of type struct student_s, but you don't want to define the student variable here, as that would make it global.

然后删除此行:

struct student_s anotherStudent;

最后，在使用它们之前，先在main()中声明这两个变量:

And finally, declare both variables in main() before using them:

int main(void)
{
    struct student_s student;
    struct student_s anotherStudent;

    student.name = "Agnes McGurkinshaw";
    student.age = 97;
    student.height = 1.64;
    student.next = &anotherStudent;

    anotherStudent.name = "Jingwu Xiao";
    anotherStudent.age = 21;
    anotherStudent.height = 1.83;
    anotherStudent.next = NULL;

    printStudents(&student);
    return EXIT_SUCCESS;
}

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