struct outputs are being overwritten by last user input - c

Question

Im a beginner to C and I'm having trouble with structs.
after I've asked user for all attributes, id like to print all the values of the struct. The problem is that after I've got input all the attributes to a struct and it loops back again to ask for attributes a second time, the first struct input gets replaced by the second struct input.
I'm pretty sure that I'm allocating the same memory space over and over and thus causing the problem but I'm stuck on how to fix it. Id appreciate any advice on what i can do. thanks!
case 2:
printf ("Please input a SKU number:");
scanf ("%d", &item[MAX_ITEMS].sku_);
printf ("Quantity:");
scanf ("%d", &item[MAX_ITEMS].quantity_);
printf ("Price:");
scanf ("%f", &item[MAX_ITEMS].price_);
printf ("The item is successfully added to the inventory");
break;
to print out the sku, quantity and price
switch (menuSelection) {
case 1:
printf ("Inventory\n");
printf ("=========================================\n");
printf ("Sku Price Quantity\n");
for (i =0 ; i<=MAX_ITEMS; i++){
printf ("%d %.2f %d\n", item[i].sku_, item[i].price_, item[i].quantity_);
}
printf ("=========================================\n");
break;
here is my whole code:
#include <stdio.h>
#define MAX_ITEMS 10
struct Item{
int sku_;
float price_;
int quantity_;
}item[MAX_ITEMS];
int main (void) {
int size=0;
int menuSelection;
int i=0;
printf ("Welcome to the Shop\n");
printf ("===================");
do {
printf ("\nPlease Select from the following options:\n");
printf ("1) Display the inventory.\n");
printf ("2) Add to shop.\n");
printf ("0) Exit.\n");
printf ("select:");
scanf ("%d", &menuSelection);
if (menuSelection <0 && menuSelection >2){
printf ("Invalid input, try again: Please select from the following options:");
}
else {
switch (menuSelection) {
case 1:
printf ("Inventory\n");
printf ("=========================================\n");
printf ("Sku Price Quantity\n");
for (i =0 ; i<=MAX_ITEMS; i++){
printf ("%d %.2f %d\n", item[i].sku_, item[i].price_, item[i].quantity_);
}
printf ("=========================================\n");
break;
case 2:
printf ("Please input a SKU number:");
scanf ("%d", &item[size].sku_);
printf ("Quantity:");
scanf ("%d", &item[size].quantity_);
printf ("Price:");
scanf ("%f", &item[size].price_);
printf ("The item is successfully added to the inventory");
break;
case 3:
break;
}
}
} while (menuSelection != 0);
return 0;
}

Answer 1

You create an array of Item objects with the length of MAX_ITEMS, currently being 10. That is, your objects have the indices of 0 to 9. Yet when asking the user for input, you always store the data at item[MAX_ITEMS] which is out of bounds of your array.
As a side note, when printing your array, you always print it whole, meaning also uninitialised items.
You have to store how many items are already "added to the shop" and use this number to determine the next array index where user input has to be stored. When printing you only have to iterate over the items already stored. Don't forget bounds checking, e.g. don't allow new user input when your shop is full.

Answer 2

The problem is that you always save the new values in the same place:
item[MAX_ITEMS].sku_
Instead, you should have a counter that show how many items are stored and save the new values in the place that is equal to the counter:
item[counter].sku_
and after every insertion you should increase the counter:
counter++;
So, your code should look like this:
int counter=0;
...
case 2:
printf ("Please input a SKU number:");
scanf ("%d", &item[counter].sku_);
printf ("Quantity:");
scanf ("%d", &item[counter].quantity_);
printf ("Price:");
scanf ("%f", &item[counter].price_);
printf ("The item is successfully added to the inventory");
counter++;
break;
I hope I was helpful

Answer 3

The item you defined is a array with size of MAX_ITEMS, so the problem of you is not about struct but array.
In most of computer programming language, indexing an array should use a offset start on zero. That is, MAX_ITEMS of item[MAX_ITEMS] is out of range for the array, you got a bug and do not find it. When you adding a item to your shop, you should code like this:
case 2:
if (last < MAX_ITEMS - 1)
{
printf ("Please input a SKU number:");
scanf ("%d", &item[last].sku_);
// ...
last ++; // on success
}
else
{
print("oops, shop is full.");
}