Resizing an array within a class

Question

I have an issue that's been bothering me.

I have an assignment to do which involves creating a program that does several tasks, using OOP.

The assignment is creating a shopping cart using separate classes and one of the tasks is to eliminate one item from the class.

I have it set it up like this.

Product class is:

class Product
{
    private string name;
    private decimal price;

    public Product(string name, decimal price)
    {
        this.name = name;
        this.price = price;
    }

Shopping cart class is:

class ShoppingCart
{
    private Product[] products;

    public ShoppingCart(Product[] products)
    {
        this.products = products;
    }

To remove the last item, I'm trying this within the ShoppingCart class.

public void RemoveLastProductFromCart()
{
   Array.Resize(ref products, products.Length - 1);
}

But it's not resizing the Product[] products and I cannot find another way to do so. I have to use arrays because we haven't gotten to lists yet.

EDIT: This is the test I have to check if the resizing works, and the function is called:

        [TestMethod]
    public void ShouldRemoveLastProductInCart()
    {
        Product[] products =
        {
          new Product("Milk", 12.10m),
          new Product("Meat", 14.15m)
        };

        ShoppingCart cart = new ShoppingCart(products);
        cart.RemoveLastProductFromCart();
        Assert.AreEqual(1, products.Length);
    }

Arrays are fixed length by definition, aren't they? You can write a method that returns another array containing the remaining items of the previous array — JustAPup, Mar 10 '16 at 21:52
@Eser Read the post. He has to use an array for this assignment — LaneL, Mar 10 '16 at 21:54
@ScottChamberlain I have to use arrays. I would very much like to use List, but not allowed yet. — Mervian O. Robert, Mar 10 '16 at 21:55
@LaneL I read it. where is the condition of using array..... — Eser, Mar 10 '16 at 21:55
@LaneL "I have to use arrays because we haven't gotten to lists yet." Last sentence. — Mervian O. Robert, Mar 10 '16 at 21:55
@NathanCooper Yes. Not yet. Tutor said we're going to get there in a couple of days, but I'm not allowed to research it myself and use it. It's a step by step course. — Mervian O. Robert, Mar 10 '16 at 21:57
Are you sure you've actually *called* `RemoveLastProductFromCart()`? — Glorin Oakenfoot, Mar 10 '16 at 21:57
The .resize does indeed change the list, but it does not update the references to the array, reassign whatever reference you are using to the array after you remove the last item and see if the changes persist. — detellda, Mar 10 '16 at 21:57
I am guessing you are in the same class as HereToLearn, he just asked [a similar question about arrays](http://stackoverflow.com/questions/35927470/correct-way-to-add-byte-variables-into-byte-arrays) and said he was not allowed to use lists either. — Scott Chamberlain, Mar 10 '16 at 21:58
It's dirty, but you could just create a new array and copy the contents of the initial array into the new shorter array. — ManoDestra, Mar 10 '16 at 21:59
@GlorinOakenfoot see this http://stackoverflow.com/questions/327916/redim-preserve-in-c — detellda, Mar 10 '16 at 21:59

score 5 · Accepted Answer · answered Mar 10 '16 at 22:01

5

The problem is your test, once you called Array.Resize the array the products variable in ShouldRemoveLastProductInCart and the array in cart.products are no longer the same array in memory.

If you made your test check cart.products size you would see a correct value of 1.

answered Mar 10 '16 at 22:01

Scott Chamberlain

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Damn. I really didn't see that. Thank you very much. Works now. – Mervian O. Robert Mar 10 '16 at 22:08

Resizing an array within a class

1 Answers1