Instantiate an object in a prefab?

Question

I have a setup with some nodes to form a path for a moving platform, each with a custom editor UI button to instantiate the currently selected node, and set the newly made node as the next node in the path. This works fine, except it breaks when I try to make a prefab of the setup so I can drag-and-drop in more moving platforms later.

When I make it a prefab, everything seems fine at first - I can make a new node, and it's set as the next one along the path. However, the editor doesn't mark the first node as having been modified from the prefab, so when I hit play it reverts to the prefab - and the connection to the new node breaks. If I drag and drop in the new node as reference it works fine, but I wanted to try and make the button do all the work so I wouldn't need to worry about having to drag and drop for every node.

Is there a way to force the prefab to recognize that there's been an update when pressing the button? I'm guessing it's just not recognizing it, since I'm using custom UI. Is there a more graceful way to fix this?

Answer 1

Answer by newbdragoon · Sep 13, 2020 at 07:47 PM

Thanks for the help! I managed to get it working with customClass = (customClass)target and PrefabUtility.RecordPrefabInstancePropertyModifications - however, I'm not using SerializedProperty and SerializedObject since I didn't really realize that they were better to use, and I don't have any experiecne using them. Since I'm not using them, though, I can't Undo the creation of the new pathing nodes. This isn't the worst thing in the universe, but it would be nice. I tried a few different things with SerializedObject and couldn't quite figure out how to get it working, can anyone shed some light on what I might be doing wrong? Here's the relevant code, without using SerializedObject since I'm not sure how to correctly implement it:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEditor;
 
 [CustomEditor(typeof(PlatformPathNode))]
 public class PlatformPathNodeUI : Editor
 {
     public override void OnInspectorGUI()
     {
         PlatformPathNode thisNode = (PlatformPathNode)target; //grabs the current object
 
         if (GUILayout.Button("Create New Node"))
         {
             int c = thisNode.transform.parent.childCount;
             Instantiate(thisNode.transform.GetComponent<PlatformPathNode>(), thisNode.transform.parent); //creates a clone of this node with the same parent
             PlatformPathNode newNode = thisNode.transform.parent.GetChild(c).GetComponent<PlatformPathNode>(); //grab the new node
             newNode.name = "Node " + (c - 1); //renames the new node to show its number in the child hierarchy
 
             thisNode.nextNode = newNode; //sets the newly made node as the next one in the path
 
             PrefabUtility.RecordPrefabInstancePropertyModifications(thisNode);
             Selection.activeObject = thisNode.nextNode; //set the new node as active
 
         }
     }
 }

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Capricornum · Sep 13, 2020 at 09:42 PM 0

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Too be honest I don't quite manage to follow along. Do you really need this connection via thisNode.nextNode? Everything is connected as next child within a transform anyhow isn't it? So you could just access it later by calling this from the Parent Transform:

 foreach (Transform child in transform)
 {
 PlatformPathNode node = child.GetComponent<PlatformPathNode>();
 node.DoSomeStuff();
 }

Then you don't need to make any references at all. You can happily create your nodes in the scene, no?

Capricornum · Sep 13, 2020 at 09:54 PM 1

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However there is an actual Undo class within Unity. You can find it HERE. So try writing Undo.RecordObject(thisNode, "Change on Node") as the first thing in your GUILayout.Button part. $$anonymous$$aybe that's all you need.

Also how about this:

 if (GUILayout.Button("Create New Node))
 {
 Undo.RecordObject(thisNode, "Change on Node");
 PlatformPathNode newNode = Instantiate(thisNode, thisNode.transform.parent);
 newNode.index = thisNode.index + 1;
 thisNode.nextNode = newNode;
 PrefabUtility.RecordPrefabInstanceblablalba;
 Selection.activeSelection = blablabla;
 }

Capricornum · Sep 13, 2020 at 09:56 PM 0

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I am not experienced enough with SerializedProperty and SerializedObject to help you with that.

Instantiate an object in a prefab?

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