Copying ScriptableObjects

Question

Is there a way of mimicking MonoBehaviour copy semantics in ScriptableObjects?

Say I have a MonoBehaviour like so:

public class DummyClassBehaviour : MonoBehaviour {
    public DummyClass           DummyClassTest;     //ScriptableObject
    public DummyClassBehaviour  DummyBehaviourTest; //Another DummyClassBehaviour
}

And a ScriptableObject:

public class DummyClass : ScriptableObject {
    public string Text = "";
}

When I duplicate(CTRL+D) a GameObject w/ DummyClassBehaviour attached, 'DummyBehaviourTest' copies as you would expect: If it references a MonoBehaviour in the GameObject I'm copying, the copy mechanism updates the reference to the same MonoBehaviour type in the new GameObject. If it references a MonoBehaviour in another GameObject, that reference remains unchanged.

The ScriptableObject, on the other hand, always references the original. So I end up with N GameObject's all sharing the same ScriptableObject (DummyClass) from the original GameObject. I'm using ScriptableObjects to allow serialization of non-Monobehaviour data classes.

Answer 1

As far as I can tell, and please someone correct me if I'm wrong, you cannot modify the serialization behavior of a ScriptableObject to match that of a MonoBehaviour. Namely that it should update references if a duplicate is made.

Instead I opted for a less than optimal solution, but it works. My class is assigned a unique identifier that gets serialized like everything else. I use this ID in DummyBehaviour.Awake() to create a lookup table that I can then use to reassign my DummyClass.

I'm not going to accept my own answer because I don't feel it answers my original question fully, but it's related:

[System.Serializable]
public class DummyClass {
// Unique id is assigned by DummyBehaviour and is unique to the game object
    // that DummyBehaviour is attached to.
public int UniqueID = -1;
public string Text = "";

// Override GetHashCode so Dictionary lookups 
public override int GetHashCode(){
    int hash = 17;
        hash = hash * 31 + UniqueID;
    return hash;
}

    // override equality function, allows dictionary to do comparisons.
public override bool Equals(object obj)
{
    if (object.ReferenceEquals(obj, null))return false;

    DummyClass item = obj as DummyClass;
    return item.UniqueID == this.UniqueID;
}

    // Allow checks of the form 'if(dummyClass)'
public static implicit operator bool(DummyClass a) 
{
    if (object.ReferenceEquals(a, null)) return false;
    return (a.UniqueID==-1)?false:true;
}


public static bool operator ==(DummyClass a, DummyClass b)
{
    if (object.ReferenceEquals(a, null))
    {
         return object.ReferenceEquals(b, null);
    }

    return a.Equals(b);
}
public static bool operator !=(DummyClass a, DummyClass b)
{
    if (object.ReferenceEquals(a, null))
    {
         return object.ReferenceEquals(b, null);
    }
    return !a.Equals(b);
}
}

And my MonoBehaviour:

[ExecuteInEditMode]
public class DummyBehaviour : MonoBehaviour {
    public List<DummyClass> DummyClasses = new List<DummyClass>();

    // reassign references based on uniqueid.
    void Awake(){   
        Dictionary<DummyClass,DummyClass> dmap = new Dictionary<DummyClass,DummyClass>();
        // iterate over all dummyclasses, reassign references.
        for(int i = 0; i < DummyClasses.Count; i++){
            DummyClass2 d = DummyClasses[i];
            if(dmap.ContainsKey(d)){
                DummyClasses[i] = dmap[d];
            } else {
                dmap[d] = d;
            }
        }
        DummyClasses[0].Text = "All items same";
    }

    // helper function, for inspector contextmenu, to add more classes from Editor
    [ContextMenu ("AddDummy")]
    void AddDummy(){
        if(DummyClasses.Count==0)DummyClasses.Add(new DummyClass{UniqueID = 1});
        else {
            // Every item after 0 points to zero, serialization will remove refs during deep copy.
            DummyClasses.Add(DummyClasses[0]);
        }
        UnityEditor.EditorUtility.SetDirty(this);
    }
}