AssetDatabase.TryGetGUIDAndLocalFileIdentifier

Parameters

Returns

bool True if the guid and file id were successfully found, false if not.

Description

Get the GUID and local file id from an object instance id.

When Unity serializes an asset reference it points to two things: the GUID and file ID. GUID is a unique hash, and file ID is a value relative to the asset. Both of these values are used when a serialized asset references another asset.

If working with a text serialized project (see Editor Settings) it is possible to manually modify this information. A common use is moving C# script files from a project to a DLL while keeping any GameObjects using these scripts intact. As an example, suppose your project contains a C# MonoBehaviour, a Scene, and a GameObject with this script attached. When serialized the Unity scene file will contain something that looks like this (reduced to the relevant parts):

no example available in JavaScript

/* example .unity scene contents:

--- !u!1 &65078845
GameObject:
  m_Component:
  -component: {fileID : 65078850}
--- !u!114 &65078850
MonoBehaviour:
  m_Script: {fileID : 11500000, guid : 9cbd8cdf99d44b58972fbc7f6f38088f, type : 3}

*/

Currently the m_Script field is pointing to the MyScript.cs GUID and file ID.

Now suppose you want to compile MyScript.cs to a DLL and remove MyScript from your project (since it's already compiled in a DLL). Removing MyScript.cs will break any MonoBehaviour references even though it still exists in DLL form. That is because the GUID and FileId of the MyScript behaviour are no longer the same. To fix this state, use TryGetGUIDAndLocalFileIdentifier with the DLL to retrieve the new asset ids, then find and replace the m_Script references to the old MyScript.cs.

no example available in JavaScript

using System.Text;
using System.Collections;
using UnityEngine;
using UnityEditor;

class ShowAssetIds
{
    [MenuItem("Assets/Show Asset Ids")]
    static void MenuShowIds()
    {
        var stringBuilder = new StringBuilder();

        foreach (var obj in AssetDatabase.LoadAllAssetsAtPath(AssetDatabase.GetAssetPath(Selection.activeObject)))
        {
            string guid;
            int file;

            if (AssetDatabase.TryGetGUIDAndLocalFileIdentifier(obj, out guid, out file))
            {
                stringBuilder.AppendFormat("Asset: " + obj.name +
                    "\n  Instance ID: " + obj.GetInstanceID() +
                    "\n  GUID: " + guid +
                    "\n  File ID: " + file);
            }
        }

        Debug.Log(stringBuilder.ToString());
    }
}