UnityObjectConverter.cs

using System;
using System.Collections.Generic;
using FullSerializer;

/// <summary>
/// A Unity object converter for Full Serializer: https://github.com/jacobdufault/fullserializer
/// This converter serialises a UnityObject (such as a MonoBehaviour or GameObject)
/// as an integer index into a list maintained by a parent class which handles the *actual* serialisation.
/// This allows us to leverage Unity's built-in serialisation of UnityObjects while also having our own 
/// serialisation logic. The external list is accessed during de/serialisation via Serializer.Context.
/// This works with both scene references and asset references.
/// </summary>
public class UnityObjectConverter : fsConverter
{
    // -------------------------------------------------------------------------------

    public override bool CanProcess(Type type)
    {
        // This converter applies to any UnityEngine.Object or subclass e.g. MonoBehaviour, ScriptableObject
        var unityObjectType = typeof(UnityEngine.Object);
        return (type == unityObjectType) || (type.IsSubclassOf(unityObjectType));
    }

    // -------------------------------------------------------------------------------

    public override bool RequestCycleSupport(Type storageType)
    {
        return false;
    }

    // -------------------------------------------------------------------------------

    public override bool RequestInheritanceSupport(Type storageType)
    {
        return false;
    }

    // -------------------------------------------------------------------------------

    public override fsResult TrySerialize(object instance, out fsData serialized, Type storageType)
    {
        // Grab the list of serialised Unity objects from the Context object
        var serialisedUnityObjects = Serializer.Context.Get<List<UnityEngine.Object>>();
        var unityObjectInstance = instance as UnityEngine.Object;

        // If the Unity Object reference is null we don't need a valid index
        // into the list of serialisedUnityObjects, so just store -1 and return
        if (unityObjectInstance == null)
        {
            serialized = new fsData(-1);
            return fsResult.Success;
        }

        // Otherwise, search our existing list of object references for a match
        var serialisedUnityObjectsIndex = -1;
        for (var i = 0; i < serialisedUnityObjects.Count; i++)
        {
            if (serialisedUnityObjects[i] == unityObjectInstance)
            {
                serialisedUnityObjectsIndex = i;
                break;
            }
        }

        // If this is a new object reference that we don't already have in our list
        // add it now and serialize the new object's index in the list
        if (serialisedUnityObjectsIndex < 0)
        {
            serialisedUnityObjectsIndex = serialisedUnityObjects.Count;
            serialisedUnityObjects.Add(unityObjectInstance);
        }

        serialized = new fsData(serialisedUnityObjectsIndex);
        return fsResult.Success;
    }

    // -------------------------------------------------------------------------------

    public override fsResult TryDeserialize(fsData data, ref object instance, Type storageType)
    {
        // Grab the list of serialised Unity objects from the Context object
        var serialisedUnityObjects = Serializer.Context.Get<List<UnityEngine.Object>>();
        var serialisedUnityObjectsIndex = (int)data.AsInt64;

        // Sanity check the index we've just deserialised against the Context list
        if (serialisedUnityObjectsIndex < 0 || serialisedUnityObjectsIndex >= serialisedUnityObjects.Count)
        {
            return fsResult.Warn("Invalid Unity Object reference index, could not deserialise!");
        }

        instance = serialisedUnityObjects[serialisedUnityObjectsIndex];
        return fsResult.Success;
    }

    // -------------------------------------------------------------------------------

    public override object CreateInstance(fsData data, Type storageType)
    {
        // We never want the serialiser to create Unity objects, null references are fine!
        return null;
    }

    // -------------------------------------------------------------------------------
}