Making a copy from an object of a list and add it to another list

Hi everyone,

I have two lists.
One is a list which hold all items available in game. (weaponList)
And another one which holds items that you actually have in your inventory. (weaponInPossession)

I now want to add a specific object from weaponList to weaponInPossession, which I do with the following code:

Code (CSharp):

1. WeaponList.weaponInPossession.Add(WeaponList.weaponList[weaponID]);

However, what I have noticed is that, if I add the same object several times to the list, the objects are all linked, meaning if I change a value of one object, all the others change to.
I suppose it's only a reference, instead of a new object.

Unfortunately I can't just write "new" in front of it, so is there a way to solve this?

 

struct

s pass by value,

class

es are passed by reference. So the question is, what do these lists contain - Unity objects (GameObjects, MonoBehaviours, prefabs), standard C# classes or standard C# structs?

That depends on what the lists contains.

Yes; a few potential options include :- copy constructors, cloning, Unity's

Instantiate()

. It all depends on what's in the lists.

 

As you said, all your list entries reference the same object.

To create a copy (aka clone), create an extension method:

Code (CSharp):

1. /// <summary>
2. /// Perform a deep Copy of the object.
3. /// </summary>
4. /// <typeparam name="T">The type of object being copied.</typeparam>
5. /// <param name="source">The object instance to copy.</param>
6. /// <returns>The copied object.</returns>
7. public static T Clone<T>(this T source)
8. {
9.     if (!typeof(T).IsSerializable)
10.     {
11.         throw new ArgumentException("The type must be serializable.", "source");
12.     }
13.  
14.     // Don't serialize a null object, simply return the default for that object
15.     if (Object.ReferenceEquals(source, null))
16.     {
17.         return default(T);
18.     }
19.  
20.     IFormatter formatter = new BinaryFormatter();
21.     Stream stream = new MemoryStream();
22.     using (stream)
23.     {
24.         formatter.Serialize(stream, source);
25.         stream.Seek(0, SeekOrigin.Begin);
26.         return (T)formatter.Deserialize(stream);
27.     }
28. }

Usage:

Code (CSharp):

1. WeaponList.weaponInPossession.Add(WeaponList.weaponList[weaponID].Clone());

 

The list contains a class which contains ints, floats, strings, bools, Sprites.

@Stefan-Laubenberger
It gives me the error message Unity.Sprite is not marked as Serializable.
However, I have my complete class marked as serializable:

Code (CSharp):

1. [System.Serializable]
2. public class weaponListClass
3. {
4.     public string name { get; set; }
5.     public Sprite itemSp { get; set; }
6.     public int minAtk { get; set; }
7.     public int maxAtk { get; set; }
8.     public float acc { get; set; }
9.     public float cost { get; set; }
10.     public int weight { get; set; }
11.     public int itemSpace { get; set; }
12.     public Sprite type1 { get; set; }
13.     public Sprite type2 { get; set; }
14.     public bool equipped { get; set; }
15.     public int itemType { get; set; } //0 weapon, 1 item, 2 equip, 3 ring
16.     public string itemDescription { get; set; }
17.     public float usingCost { get; set; }
18.     public int ml { get; set; }
19. }

 

You'll need some form of cloning. I couldn't get the serialisation cloning method to work with the Sprite. I did find this serialisation solution but don't know anything about it to actually recommend it.

You could just implement a Clone() method directly in weaponListClass that copies all internals with the exception of the Sprite that can just reuse the same reference.