Synch Parent

using Fusion;
using UnityEngine;

// This component will sync parenting of a transform,
// using either a NetworkObject or NetworkBehaviour reference.
public class WrapUnwrapSample : NetworkBehaviour
{

  // Networked NetworkObject with auto properties:
  // The ILWeaver replaces the Get method with code which writes the NetworkId
  // to the snapshot, and the Set method with handling which finds the Object using the NetworkId.
  // Get will return the Object if found.
  // Get will return null if the property was set to null, and also will return null if the Object could not be found.
  [Networked] public NetworkObject    MyNetworkObject    { get; set; }

  // Networked NetworkBehaviour with auto properties:
  // The ILWeaver replaces the Get method with an implementation which writes the NetworkBehaviourId
  // to the snapshot, and the Set method implementation which finds the Object using the NetworkBehaviourId.
  // Get will return the Object if found.
  // Get will return null if the property was set to null, and also will return null if the Object could not be found.
  [Networked] public NetworkBehaviour MyNetworkBehaviour { get; set; }

  // NetworkId is backed by one int value.
  // Zero represents null/Invalid.
  [Networked] public NetworkId ParentNetId { get; set; }

  // NetworkBehaviourId is backed by two values:
  // Object = The NetworkId of the NetworkObject
  // Behaviour = NetworkBehaviour index in the hierarchy of the NetworkObject.
  [Networked] public NetworkBehaviourId ParentNBId { get; set; }

  public override void FixedUpdateNetwork()
  {
    if (Object.HasStateAuthority)
    {
      CaptureParent();
    }
    else
    {
      ApplyParent();
    }
  }

  private void CaptureParent()
  {
    var parent = transform.parent;

    // If the current parent is null, set the Object value to default (0).
    // This represents null.
    if (parent == null)
    {
      ParentNetId = default;
      ParentNBId = default;
      return;
    }

    // Find a NetworkBehaviour on the parent and capture its NetworkId.
    var parentNB =  parent.GetComponent<NetworkBehaviour>();
    if (parentNB != null)
    {
      ParentNBId  = parentNB.Id;
      ParentNetId = default;
    }
    // if the parent does not have a NetworkBehaviour component,
    // find a NetworkObject instead.
    else
    {
      var parentNO = parent.GetComponent<NetworkObject>();
      if (parentNO != null) {
        ParentNetId = parentNO.Id;
        ParentNBId = default;
      }
      else
      {
        Debug.LogWarning("Parent on StateAuthority does not have a NetworkObject or NetworkBehaviour. Cannot be identified and serialized.");
        ParentNetId = default;
        ParentNBId  = default;
      }
    }
  }

  private void ApplyParent()
  {
    // Test for an NetworkId == 0 (same as Invalid),
    // which represents an explicit null value.
    if (ParentNBId.Object.IsValid == false && ParentNetId.IsValid == false)
    {
      transform.SetParent(null);
      return;
    }

    // If the parent was a NetworkObject Id, try to unwrap it.
    if (ParentNetId.IsValid)
    {
      if (Runner.TryFindObject(ParentNetId, out var parentNO))
      {
        transform.SetParent(parentNO.transform);
      }
      else
      {
        Debug.LogWarning($"NetworkObject:{ParentNBId.Object} not found on the local runner. " +
                         "NetworkObject is possibly out of Interest.");
        transform.SetParent(null);
      }
      return;
    }

    // if the parent was a NetworkBehaviour, try to unwrap it.
    if (ParentNBId.IsValid)
    {
      if (Runner.TryFindBehaviour(ParentNBId, out var parentNB))
      {
        transform.SetParent(parentNB.transform);
      } else
      {
        Debug.LogWarning($"NetworkObject:{ParentNBId.Object} NB:{ParentNBId.Behaviour} not found on the local runner. " +
                         "NetworkObject is possibly out of Interest.");
        transform.SetParent(null);
      }
    }
  }
}