쫌 꼼수지만 아래와 같이 작동한다.

참조 바로가기 

        PrefabUtility.DisconnectPrefabInstance(obj);
        Object prefab = PrefabUtility.CreateEmptyPrefab("Assets/dummy.prefab");
        PrefabUtility.ReplacePrefab(obj, prefab, ReplacePrefabOptions.ConnectToPrefab);
        PrefabUtility.DisconnectPrefabInstance(obj);
        AssetDatabase.DeleteAsset("Assets/dummy.prefab");

계층뷰 상의 여러개의 프리펩 오브젝트들을 한번 Apply 하는 것을 제작 하였습니다.

  
using UnityEngine;
using UnityEditor;
using System.Collections;
using System.Collections.Generic;

public class csPrefabApplyer
{
    [MenuItem("GameObject/CustomMenu/Apply Prefabs", false, 0)]
    static void Init(MenuCommand menuCommand)
    {
        if (Selection.objects.Length > 0)
        {
            if (menuCommand.context == Selection.objects[0])
            {
                GameObject[] prefabs = Selection.gameObjects;

                Dictionary _prefabDicList = new Dictionary();
                for (int i = 0; i < prefabs.Length; i++)
                {
                    // 프리펩이 아닌 오브젝트는 무시
                    if (PrefabUtility.GetPrefabParent(prefabs[i]) != null)
                    {
                        // 최상위 부모가 아닐때 최상위 부모를 검색하여 추가
                        GameObject root = PrefabUtility.FindRootGameObjectWithSameParentPrefab(prefabs[i]);
                        if (!_prefabDicList.ContainsKey(root.name))
                        {
                            _prefabDicList.Add(root.name, root);
                        }
                    }
                    else if (PrefabUtility.GetPrefabParent(prefabs[i]) == null && PrefabUtility.GetPrefabObject(prefabs[i]) != null)
                    {
                        // 최상위 부모일때 추가
                        GameObject target = PrefabUtility.GetPrefabObject(prefabs[i]) as GameObject;
                        if (!_prefabDicList.ContainsKey(target.name))
                        {
                            _prefabDicList.Add(target.name, target);
                        }
                    }
                }

                // 갱신
                foreach (KeyValuePair prefab in _prefabDicList)
                {
                    PrefabUtility.ReplacePrefab(prefab.Value, PrefabUtility.GetPrefabParent(prefab.Value), ReplacePrefabOptions.ConnectToPrefab);
                }
                return;
            }
        }
    }
}

1. How to execute MenuItem for multiple objects once.

1. static public void MethodName(MenuCommand menuCommand)
2. {
3. //Prevent executing multiple times when right-clicking.
4. if (Selection.objects.Length > 1)
5. {
6. if (menuCommand.context != Selection.objects[0])
7. {
8. return;
9. }
10. }
11. }

윗코드에선 두개의 오브젝트를 선택했을때 첫번째 인덱스 0의 오브젝트와 같으면 패스하게 되고 나머지 오브젝트들을 다실행하는데 하나만 실행 되게 하기 위해선 아래와 같이 수정이 필요 했다.

        if (Selection.objects.Length > 0)
        {
            if (menuCommand.context == Selection.objects[0])
            {
                    return;
            }
        }

동적 프리펩 갱신 아래를 사용하자

  PrefabUtility.ReplacePrefab( go, PrefabUtility.GetPrefabParent( go ), ReplacePrefabOptions.ConnectToPrefab );

using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 #if UNITY_EDITOR
 using UnityEditor;
 #endif
 
 public class UnitEditorBulkApply : MonoBehaviour, ICheckForUnsafeChanges
 {
     public bool resetPosition = true;
     public bool resetScale = true;
     public bool resetRotation = true;
 
 
 #if UNITY_EDITOR
     [ContextMenu("Apply Bulk Prefab Apply")]
     public void CheckForUnsafeChanges()
     {
         for ( int i = 0; i < transform.childCount; i++)
         {
             GameObject go = transform.GetChild( i ).gameObject;
 
             if ( PrefabUtility.GetPrefabParent( go ) != null )
             {
                 Vector3 pos = go.transform.localPosition;
                 Vector3 scale = go.transform.localScale;
                 Quaternion rot = go.transform.localRotation;
 
                 if ( resetPosition ) go.transform.localPosition = Vector3.zero;
                 if ( resetScale ) go.transform.localScale = Vector3.one;
                 if ( resetRotation ) go.transform.localRotation = Quaternion.identity;
 
                 {
                     MonoBehaviour [] behaviours = go.GetComponents<MonoBehaviour>();
                     foreach ( MonoBehaviour b in behaviours )
                         if ( b is ICheckForUnsafeChanges )
                             ( b as ICheckForUnsafeChanges ).CheckForUnsafeChanges();
                 }
 
                 Debug.Log( "Applying changes to " + go.name, go );
                 PrefabUtility.ReplacePrefab( go, PrefabUtility.GetPrefabParent( go ), ReplacePrefabOptions.ConnectToPrefab );
 
                 if ( resetPosition ) go.transform.localPosition = pos;
                 if ( resetScale ) go.transform.localScale = scale;
                 if ( resetRotation ) go.transform.localRotation = rot;
             }
         }
     }
 #endif
 }
 
 public interface ICheckForUnsafeChanges {
 #if UNITY_EDITOR
     void CheckForUnsafeChanges();
 #endif
 }