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--- globalobjectid [2021/02/08 08:26] – uninomiconadmin
+++ globalobjectid [2025/01/15 04:35] (current) – external edit 127.0.0.1
@@ Line 9: / Line 9: @@
 //All notes below only apply to running the game in Play mode in the Editor.//
-Prefabs Instances have a GID value that is different from the GID assigned when the game is run in Play Mode. When a scene is loaded in play mode, prefabs are merged (unpacked) into standard game-objects. These gameobjects have a different GID than the original prefab. However the GID of the unpacked GameObjects is *still* unique and stable!
+When a scene is loaded in play mode, prefabs are unpacked ((I've seen this mentioned in the profiler as Prefabs.MergePrefabs, during [[scenemanager]] scene loads.)) into standard game-objects. These gameobjects have a different GID than the original prefab. However the GID of the unpacked GameObjects is *still* unique and stable!
-Whatever process that Unity uses to unpack gameobjects((
-I've seen this mentioned in the profiler as Prefabs.MergePrefabs, during [[engine:scenemanager]] scene loads.
-)) must be determinstic, and generate a fileID for the new gameobject that is based on the prefab.
 For example. You may have a prefab in the scene with GID:
@@ Line 27: / Line 23: @@
 ==== Converting a Prefab Gid to an Unpacked Gid ====
-You can convert between the two using the following formula:((https://forum.unity.com/threads/how-is-fileid-generated-for-m_correspondingsourceobject.726704/#post-4851011))
+You can convert between the two using the following formula:((
+Source: [[https://forum.unity.com/threads/how-is-fileid-generated-for-m_correspondingsourceobject.726704/#post-4851011]]  This is for a slightly different situation, but I have found that the same formula applies to unpacking prefabs
+))
 ''%%(%%prefabGid.targetObjectId ^ prefabGid.targetPrefabId) & 0x7fffffffffffffff''
+++++ Example Code|
+<code csharp>
+private static GlobalObjectId ConvertPrefabGidToUnpackedGid(GlobalObjectId id)
+{
+    ulong fileId = (id.targetObjectId ^ id.targetPrefabId) & 0x7fffffffffffffff;
+    bool success = GlobalObjectId.TryParse(
+        $"GlobalObjectId_V1-{id.identifierType}-{id.assetGUID}-{fileId}-0",
+        out GlobalObjectId unpackedGid);
+    Assert.IsTrue(success);
+    return unpackedGid;
+}
+</code>
+++++
+===== Bug: Querying deleted objects =====
+When calling ''GlobalObjectId.GlobalObjectIdentifiersToObjectsSlow'' with a GlobalObjectId that was assigned to a now-deleted object, the Object returned will sometimes be a valid, arbitrary Object in the project, rather than the correct value of ''null''.
+For example, in this case, when passed an array of only scene objects:
+{{ :hdmvjaumtf.png?direct&400 |}}
+The function will return non-scene objects (the shader editor asset at 205).
+{{ :is0bzbpnb6.png?direct&400 |}}
+This seems to be a bug. The correct result should have been ''null'', because that GID was deleted.
+I have had some luck <sup>[//[[:wiki:tag:dark-magic|dark magic]]//]</sup> querying these 'bad' GIDs individually with ''GlobalObjectIdentifierToObjectSlow''. This seems to properly return null in certain cases. This does not cure all cases, however((Luckily, there was only a small set of objects that were valid to be stored by my GIDs, and so I could discard any GIDs resolving to the wrong type.)).
+Update: This is fixed in 2021.1 [[https://issuetracker.unity3d.com/issues/globalobjectidglobalobjectidentifierstoobjectsslow-sometimes-returns-a-random-existing-gameobject|bug tracker]].