How do you assign values entered in a structure to an array? - c

Question

I'm having a little trouble doing this. I'm creating a program that will store individuals information by ID number using a structure. I need to store then in an array then search through it with a for loop (easy). Whenever I try to compile I get an error saying request for member "blah blah" in something not a structure or union.
I'm getting this error for the final printf statement.
#include <stdio.h>
#include <stdlib.h>
struct infoStruct
{
int studentID;
int year;
int month;
int day;
int phone;
int end;
};
int main (void)
{
int students = 0;
struct infoStruct *info = NULL;
while (info.end != -1) {
students = students + 1;
printf("Enter student information (ID, day, month, year, phone)\n");
printf("Enter -1 following the phone number to end the process to continue enter 0\n");
info = malloc(sizeof(struct infoStruct) * students);
scanf("%d %d %d %d %d %d", &info.studentID, &info.day, &info.month, &info.year, &info.phone, &info.end);
}
printf("You entered %d student(s)\n", students);
printf("Enter Student ID\n");
scanf("%d", info.studentID);
}

Answer 1

First, your array should be of type infoStruct.
You should know the value of students. Then you can do something like:
for (int i=0;i<students;++i)
{
scanf(%d %d"[...],&infoArray[i].studentID, &infoArray[i].year[...]);
}

Answer 2

"info" is a pointer. So to access its values you should unreference it. As you are using array of struct you can do it in the following way:
scanf("%d %d %d %d %d %d", &info[some_counter].studentID, &info[some_counter].day, &info[some_counter].month, &info[some_counter].year, &info[come_counter].phone, &info[come_counter].end);
Also it is better to use realloc() call to change size of array of structs and fix in some way end of loop condition. Now it makes a crash because info is NULL and right before start you are trying to dereference this NULL pointer.
Loop with realloc() may look like following code:
while (true) {
printf("Enter student information (ID, day, month, year, phone)\n");
printf("To finish enter word \"end\"\n");
struct infoStruct *new_info = realloc(info, (students+1)*sizeof(struct infoStruct));
if (new_info == NULL) {
printf("Out of memory! errno = %s\n", strerror(errno));
break;
} else {
info = new_info;
}
result = scanf("%d %d %d %d %d %d",
&info[students].studentID,
&info[students].day,
&info[students].month,
&info[students].year,
&info[students].phone,
&info[students].end
);
if (result != 6) {
students--;
info = realloc(info, sizeof(struct infoStruct) * students);
break;
}
students++;
}

Answer 3

This:
int students = 0;
...
int infoArray [students];
...
while()
{
students = students + 1;
...
}
Will not work. You have to declare the size of your array a priori and it can't change during run-time without explicitly reallocating it.
What you can do is:
printf("What's the number of students you want?\n");
scanf("%d", &students);
...
int infoArray [students];
...
while(i++ < students)
{
// collect the data...
...
}
Since you can't change the size of the array dynamically in C without explicitly reallocating it, you will have to go for a linked list solution if you want a dynamic solution.

Answer 4

infoArray is declared a int. It does not provide structure elements like
infoArray.studentID. That causes the compiler to complain ... something not a structure or union.
infoArray [students]; with int students = 0; is questionable too.
You'd get (rewritten to suit the need. However, with some open questions):
#include <stdio.h>
#include <stdlib.h>
#define MAX_STUDENTS 200
typedef struct {
int studentID;
int year;
int month;
int day;
int phone;
int end;
} info_TYPE;
int main (void)
{
info_TYPE infoArray [MAX_STUDENTS];
int students = 0;
while (infoArray[students].end != -1) {
printf("Enter student information (ID, day, month, year, phone)\n");
printf("Enter -1 following the phone number to end the process to continue enter 0\n");
scanf("%d %d %d %d %d %d", &infoArray[students].studentID, &infoArray[students].day, &infoArray[students].month, &infoArray[students].year, &infoArray[students].phone, &infoArray[students].end);
students = students + 1;
if (students >= MAX_STUDENTS) break;
}
if (infoArray[students - 1].end = -1) printf("You entered %d student(s)\n", students);
printf("Enter Student ID", infoArray[students - 1].studentID);
// no idea what this line was for, presumably another previous attempt.
scanf("%d", infoArray[students - 1].studentID);
// getting tired to follow the speed at which the question is modified, presumably last edit here!
}

Answer 5

The compiler is complaining because
printf("Enter Student ID", infoArray.studentID);
treats infoArray.studentID as a structure member, which it is not.