Trying to delete product from my list using pointer and struct

Question

In this function, I trying to delete a product from a list. Visual Studio shows me a red line under

list->itemList[i].productName = list->itemList[i + 1].productName;

and

list->itemList[i].unit = list->itemList[i + 1].unit;

but not under

list->itemList[i].amount = list->itemList[i + 1].amount;

The productName and unit is char, and the amount is float.

void removeItem(struct ShoppingList *list){
    int itemToDelet;
    while (1) {
        for (int i = 0; i < list->length; i++) {
            printf("%d. %s \t %.2f \t %s\n", i + 1, list->itemList[i].productName, list->itemList[i].amount, list->itemList[i].unit);
        }
        printf("\n\nWhich product do you want to remove? ");
        scanf("%d", &itemToDelet);
        if (itemToDelet <= list->length) {
            for (int i = 0; i < list->length; i++) {
                if (itemToDelet == i + 1) {
                    for (int i = 0; i < list->length; i++) {
                        list->itemList[i].productName = list->itemList[i + 1].productName;
                        list->itemList[i].amount = list->itemList[i + 1].amount;
                        list->itemList[i].unit = list->itemList[i + 1].unit;
                        list->length--;
                    }
                    break;
                }
                break;
            }
        }
        else {
            printf("\nThe list contains only %d items!", list->length);
        }
        break;

    }
}

What is the definition of `struct ShoppingList`? Please add that code to your posted question. — Richard Chambers, Dec 16 '20 at 23:06
If you hover the mouse over the squiggle it should tell you what's wrong. — Barmar, Dec 16 '20 at 23:07
@LeoParden The function in any case is wrong and invokes undefined behavior. The loops within the function do not make a sense. — Vlad from Moscow, Dec 16 '20 at 23:11

score 0 · Answer 1 · answered Dec 16 '20 at 23:07

0

To copy the contents of a string (e.g. type char[10]), use strcpy. Arrays of characters cannot be assigned, just copied.

strcpy(list->itemList[i].productName,list->itemList[i + 1].productName);

answered Dec 16 '20 at 23:07

Stephan Lechner

34,891
4
35
58

score 0 · Answer 2 · answered Dec 16 '20 at 23:31

It seems that the data members productName and unit are character arrays and arrays do not have the assignment operator.

To copy strings stored in character arrays you should use the standard C function strcpy declared in the header <string.h> as for example

strcpy( list->itemList[i].productName, list->itemList[i + 1].productName );

But in any case your function is incorrect and invokes undefined behavior. The for loops within the function do not make a sense.

Instead of the for loops you could use another standard C function memmove declared in the same header <string.h> as for example

memmove( list->itemList + itemToDelet - 1, 
         list->itemList + itemToDelet,
         ( list->length - itemToDelet ) * sizeof( *list->itemList ) );

--list->length;

Also before the call of memmove you need to check that the value of itemToDelet is greater than 0.

Trying to delete product from my list using pointer and struct

2 Answers2