Correct way to nest a prefab inside another prefab from editor script?

Hi all,

What is the correct way to nest a prefab inside another prefab from editor script?

I have an editor script generating a couple hundred prefab variants. It's working well, however I'm looking to add a nested prefab to each of my variants.

Currently I am creating my variants roughly like so:

Code (CSharp):

1. // Instantiate the base prefab.
2. var basePrefabObject = PrefabUtility.InstantiatePrefab(myPrefabBaseAsset)
3. ...
4. // Create the prefab variant.
5. var variant = PrefabUtility.SaveAsPrefabAsset(basePrefabObject, outputPath)
6. ...
7. // Make some variant overrides here.
8. // This is where I would also like to add a nested prefab to the variant.
9. ...
10. // Record prefab variant modifications and save.
11. PrefabUtility.RecordPrefabInstancePropertyModifications(variant);
12. AssetDatabase.SaveAssets();
13.  
14. // Destroy instantiated base prefab object.
15. DestroyImmediate(basePrefabObject);

Thanks,
-andy.

 

Adding this should do the trick

gameObject = PrefabUtility.InstantiatePrefab(nested_prefab) as GameObject;
gameObject.transform.SetParent(variant.transform);

 

Awesome, thanks so much. I've got it working now. I was actually trying to set the transform's parent like this already but was getting the error:

"Setting the parent of a transform which resides in a Prefab is disabled to prevent data corruption."

I still get this issue when using the NestBInAViaInstances approach (perhaps I need to save the prefab first?) but using the NestBInAViaContent approach after I have first saved my variant instance works exactly as I need.

Thanks a lot!
-andy.

 

Sure, I have created a quick demo project here - https://drive.google.com/file/d/1LVp6ORKejs56R9fPVebjOFmaG9IodxlZ/view?usp=sharing.

If you use the context menu of the PrefabExample script in the scene, there are two methods "NestPrefabAfterSavingAsset (No Issues)" and "NestPrefabBeforeSavingAsset (Error)". The latter shows the error that occurs when trying to nest a prefab before it is saved. I included the working method too, where I just nest the prefab after saving, just in case.

Here is the full script in the demo project:

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3.  
4. public class PrefabExample : MonoBehaviour
5. {
6.     public GameObject basePrefab;
7.     public string outputPath;
8.     public GameObject prefabToNest;
9.  
10.     [ContextMenu("NestPrefabAfterSavingAsset (No Issues)")]
11.     public void NestPrefabAfterSavingAsset()
12.     {
13.         // Load base prefab.
14.         string basePrefabPath = AssetDatabase.GetAssetPath(basePrefab);
15.         Object basePrefabAsset = AssetDatabase.LoadAssetAtPath<Object>(basePrefabPath);
16.         GameObject basePrefabObject = (GameObject)PrefabUtility.InstantiatePrefab(basePrefabAsset);
17.  
18.         // Create prefab variant.
19.         GameObject prefabVariant = PrefabUtility.SaveAsPrefabAsset(basePrefabObject, outputPath);
20.  
21.         // I set some overrides specific to the variant here (removed).
22.  
23.         // Record modifications and save.
24.         PrefabUtility.RecordPrefabInstancePropertyModifications(prefabVariant);
25.         AssetDatabase.SaveAssets();
26.  
27.         // Clean up.
28.         DestroyImmediate(basePrefabObject);
29.  
30.         // Load the previously created prefab variant and nest the prefab.
31.         var prefabVariantContents = (GameObject)PrefabUtility.LoadPrefabContents(outputPath);
32.  
33.         // Nest the prefab.
34.         var prefabToNestObject = (GameObject)PrefabUtility.InstantiatePrefab(prefabToNest);
35.         prefabToNestObject.transform.SetParent(prefabVariantContents.transform);
36.         PrefabUtility.SaveAsPrefabAsset(prefabVariantContents, outputPath);
37.  
38.         // Clean up.
39.         PrefabUtility.UnloadPrefabContents(prefabVariantContents);
40.     }
41.  
42.     [ContextMenu("NestPrefabBeforeSavingAsset (Error)")]
43.     public void NestPrefabBeforeSavingAsset()
44.     {
45.         // Load base prefab.
46.         string basePrefabPath = AssetDatabase.GetAssetPath(basePrefab);
47.         Object basePrefabAsset = AssetDatabase.LoadAssetAtPath<Object>(basePrefabPath);
48.         GameObject basePrefabObject = (GameObject)PrefabUtility.InstantiatePrefab(basePrefabAsset);
49.  
50.         // Create prefab variant.
51.         GameObject prefabVariant = PrefabUtility.SaveAsPrefabAsset(basePrefabObject, outputPath);
52.  
53.         // I set some overrides specific to the variant here (removed).
54.  
55.         // Nest the prefab.
56.         var prefabToNestObject = (GameObject)PrefabUtility.InstantiatePrefab(prefabToNest);
57.         prefabToNestObject.transform.SetParent(prefabVariant.transform); // Generates error message.
58.  
59.         // Record modifications and save.
60.         PrefabUtility.RecordPrefabInstancePropertyModifications(prefabVariant);
61.         AssetDatabase.SaveAssets();
62.  
63.         // Clean up.
64.         DestroyImmediate(basePrefabObject);
65.     }
66. }
67.  

-andy.