Hi I have the following structure in the file structure.c #include struct studen

Question

Hi I have the following structure in the file structure.c

#include

struct student{
char *first;
char *last;
string name;
int id;
double GPA;
}

I am new to C progamming and i dont understand how I am suppose to define the following functions without instantiating the structure first

I need to define the following functions in the same c file and then enlist/declare them in the header file aswell. I am very confused as how to define these functions and how to enlist them in the header file. If someone could provide 1 example for one set method and one get method i will be very grateful. -

setName ( char* name[size])

getName()

setID(int)

getID()

setGPA(double GPA)

getGPA()

Thank you,

Explanation / Answer

You need to pass a poitner to the structure to each setter/getter function, for example

void
student_set_first_name(struct student *student, const char *const name)
{
size_t length;
if ((student == NULL) || (name == NULL))
{
fprintf(stderr, "Invalid parameters for `%s()' "), __FUNCTION__);
return;
}
/* In case we are overwriting the field, free it before
* if it's NULL, nothing will happen. You should try to
* always initialize the structure fields, to prevent
* undefined behavior.
*/
free(student->first);

length = strlen(name);
student->first = malloc(1 + length);
if (student->name == NULL)
{
fprintf(stderr, "Memory allocation error in `%s()' "), __FUNCTION__);
return;
}
memcpy(student->first, name, 1 + length);
}

const char *
student_get_first_name(struct student *student)
{
if (student == NULL)
return NULL;
return student->first;
}
  
And you could use the function like this

struct student student;
const char *first_name;

memset(&student, 0, sizeof(student));
student_set_first_name(&student, "My Name");
first_name = student_get_first_name(&student);
if (first_name != NULL)
fprintf(stdout, "First Name: %s ", first_name);
/* work with `student', and when you finish */
free(student.first);
/* and all other `malloc'ed stuff */
The good thing is that you could hide the structure definition from the library user and prevent them from misusing the structre, like setting invalid values and other things.

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