Copying multidimensional lists [SOLVED]

Questions & Answers
1

I was wondering how you would copy multidimensional lists so that one could be altered and the other not.
I want to do something like this:

public class MultidimensionalLists : MonoBehaviour
{
    private List<List<int>> list1;
    private List<List<int>> list2;

    private void Start()
    {
        list1 = new List<List<int>> { new List<int> { 0, 1, 2, 3 } };
        list2 = new List<List<int>> { new List<int> { 3, 2, 1, 0 } };

        list2.Clear();
        list2.AddRange(list1);//set list2 to list1

        //print list2[0], prints 0 1 2 3
        string result = "";
        foreach (var item in list2[0])
        {
            result += item.ToString() + " ";
        }
        Debug.Log(result); 

        list1[0].Clear();//clear list1[0]

        //print list2[0], prints a cleared list (nothing)
        result = "";
        foreach (var item in list2[0])
        {
            result += item.ToString() + " ";
        }
        Debug.Log(result);
    }

}

The problem is that when I clear list1[0], list2[0] clears as well.

2

Hey Noah,

What you are looking for is a way to deep clone a List (instead of shallow cloning).

A handy tool for this are extension methods, make a new script (e.g. “Extensions”) with the following code:

using System.IO;
using System.Runtime.Serialization.Formatters.Binary;

public static class Extensions
{
    public static T DeepClone<T>(this T obj)
    {
        using (var ms = new MemoryStream())
        {
            var formatter = new BinaryFormatter();
            formatter.Serialize(ms, obj);
            ms.Position = 0;

            return (T)formatter.Deserialize(ms);
        }
    }
}

Now you can use syntax like this:

newList = oldList.DeepClone();