Can’t serialize custom class variable in ScriptableObject.Or add instance of a class to a list with overridden method in custom editor.

Questions & Answers
1

I’m making simple inventory system. I got a class for an Item

[System.Serializable]
public class Item 
{
    public string itemName;
    public int itemId;
    //some more variables
    public Effect itemEffect;
    //some more code
public void Use(Entity x)
    {
        itemEffect.UseEffect(x);
    }
}

All the items are stored in the list inside ScriptableObject with a custom editor.
The best way of implementing item effect I came up with is this. Every item has method “Use” which is calling “UseEffect” method of itemEffect variable which is an instance of Effect class
This is the Effect class.

[Serializable]
public class Effect 
{
    public string effectName;
    public Effect ()
    {
        this.effectName = "BaseEffect";
    }

    public virtual void UseEffect (SomeParameter x)
    {
        Debug.Log("This  is base effect"+ x.Something.ToString());
    }
}

This is my Test Effect derived from Effect class

public class TestEffect: Effect
 {
    public TestEffect()
    {
        this.effectName = "TestEffect";
    }
    
    public override void UseEffect(SomeParameter x) 
    {
        Debug.Log("This is TEST EFFECT");
        x.something = x.something+1;
        Debug.Log(x.something.ToStirng());	
    }
 }

This is how i assign TestEffect object to Item variable i custom editor.

 if (GUI.Button(//someRect,"Apply test effect to test item"))
        {
          //Item_Database_Asset is the ScriptableObject  with Items_Database_List of all items                           
          Item_Database_Asset.Items_Database_List[1].itemEffect = new TestEffect();;
          EditorUtility.SetDirty(Item_Database_Asset);
          
        }

So the problem is after i click “Apply test effect to test item” when i press play and using this item it’s calling UseEffect of BaseEffect. Although in inspector i see that item[1] itemEffect.effectName is TestEffect. So is basically working but it’s still calling BaseEffect.
But if i click “Apply test effect to test item” on runtime in play mode it works fine.
It’s a bit long and convoluted.I hope it’s readable.
Thank you.

2

Unity has no polymorphism support for custom serialized classes. Read the documentation about serialization. Especially the part:

When might the serializer behave
unexpectedly?

Custom serialized classes are mainly meant to be data containers. The serializer serializes custom classes based on the variable type, not the actual type.