Defining an array list in c# unity.

Question

I am trying to make an array list of integer values and run some basic math operations as seen below.

int dice1 = 4;
int dice2 = 3;
int dice3 = 6;
int dice4 = 4;
int dice 5 = 5;

ArrayList numbers = new  ArrayList();
        numbers[4] = dice5;
        numbers[3] = dice4;
        numbers[2] = dice3;
        numbers[1] = dice2;
        numbers[0] = dice1;

numbers[3] = numbers[3] * numbers[2];

However, the computer does not allow me to do this and produces an error "Operator "*" cannot be applied to operands of the type 'object' and 'object'". How do I fix this? I think that I have to define the array list as an array of integers... however I am not too sure. Please keep the answers simple as I am quite new to C# unity.

Thanks!

Daniel Masterson · Accepted Answer · 2017-07-27 12:05:16Z

2

ArrayList stores everything as an 'object', basically the most basic type something can be in C#. You have a few options. If you want to keep using ArrayList, then you'll need to do cast the things you're multiplying, like:

numbers[3] = ((int)numbers[3]) * ((int)numbers[2])

Alternatively, you can ditch ArrayList and use the more modern List<> type. You need to add using System.Collections.Generic to the top, then your code will be like:

int dice1 = 4;
int dice2 = 3;
int dice3 = 6;
int dice4 = 4;
int dice5 = 5;

List<int> numbers = new List<int>(); //List contains ints only
    numbers[4] = dice5;
    numbers[3] = dice4;
    numbers[2] = dice3;
    numbers[1] = dice2;
    numbers[0] = dice1;

numbers[3] = numbers[3] * numbers[2]; //Works as expected

Finally, if you know that your collection will only have a certain number of things, you can use an array instead. Your code will now be:

int dice1 = 4;
int dice2 = 3;
int dice3 = 6;
int dice4 = 4;
int dice5 = 5;

int[] numbers = new int[5]; //Creates an int array with 5 elements
//Meaning you can only access numbers[0] to numbers[4] inclusive
    numbers[4] = dice5;
    numbers[3] = dice4;
    numbers[2] = dice3;
    numbers[1] = dice2;
    numbers[0] = dice1;

numbers[3] = numbers[3] * numbers[2]; //Works as expected

answered Jul 27, 2017 at 12:05

Daniel Masterson

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2 Comments

Siddharth Sengupta Over a year ago

Thank you very much for this answer. Very detailed and extremely helpful! The reason I was using ArrayLists is so that I could remove elements from it.

Daniel Masterson Over a year ago

In that case, you can also remove things from List<>. Here's a bunch of methods about it! msdn.microsoft.com/en-us/library/s6hkc2c4(v=vs.110).aspx

Jamadan · Accepted Answer · 2017-07-27 12:04:57Z

0

Avoid using array list

Use List<int> or int[]

Then the objects contained are typed instead of being object

answered Jul 27, 2017 at 12:04

Jamadan

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Comments

Ignacio Alorre · Accepted Answer · 2021-02-08 18:31:08Z

0

You can do it in one line:

List<int> numbers = new List<int>{ 4, 3, 6, 4, 5 };

answered Feb 8, 2021 at 18:31

Ignacio Alorre

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Arslan Ali · Accepted Answer · 2018-07-28 23:40:09Z

-1

You need to parse the object to string then to int value then use it with * operator.But you firstly have to initialize the arraylist with null values then assign number values So that, use following code that I made clear changes for you.

int dice1 = 4;
    int dice2 = 3;
    int dice3 = 6;
    int dice4 = 4;
    int dice5 = 5;
    int capacity=5;
    ArrayList numbers = new ArrayList(capacity);
    for (int i = 0; i < capacity;i++ )
    {
        numbers.Add(null);
    }
    numbers[4] = dice5;
    numbers[3] = dice4;
    numbers[2] = dice3;
    numbers[1] = dice2;
    numbers[0] = dice1;

    numbers[3] = (int.Parse(numbers[3].ToString()) * int.Parse(numbers[2].ToString()));
    print(numbers[3]);

answered Jul 28, 2018 at 23:40

Arslan Ali

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