Created Editor Tool

Created Editor tool to replace GameObject with Prefab

UOP1_Project/Assets/ScriptableObjects/ReplaceData.cs

+using UnityEngine;
+
+/// <summary>
+/// Data class for replace tool.
+/// </summary>
+public class ReplaceData : ScriptableObject
+{
+	// Reference to replace object.
+	public GameObject replaceObject;
+
+	// Array of object to replace.
+	public GameObject[] objectsToReplace;
+}

UOP1_Project/Assets/Scripts/Editor/ReplaceTool.cs

+using System.Linq;
+using UnityEngine;
+using UnityEditor;
+
+/// <summary>
+/// Replace tool window,available under Tools window.
+/// </summary>
+public class ReplaceTool : EditorWindow
+{
+	// Data store for replace tool.
+	ReplaceData data;
+	// Data variable wrapped into SerializedObject.
+	SerializedObject serializedData;
+	// Prefab variable from data object. Using SerializedProperty for integrated Undo.
+	SerializedProperty replaceObjectField;
+
+	private void InitDataIfNeeded()
+	{
+		// If data don't exist, create it.
+		if (!data)
+		{
+			data = ScriptableObject.CreateInstance<ReplaceData>();
+			serializedData = null;
+		}
+		// If data was not wrapped into SerializedObject, wrap it.
+		if (serializedData == null)
+		{
+			serializedData = new SerializedObject(data);
+			replaceObjectField = null;
+		}
+		// If prefab field was not assigned as SerializedProperty, assign it.
+		if (replaceObjectField == null)
+		{
+			replaceObjectField = serializedData.FindProperty("replaceObject");
+		}
+	}
+
+	// Scroll position for list of selected objects.
+	Vector2 selectObjectScrollPosition;
+
+	// Register menu item to open Window.
+	[MenuItem("Tools/Replace with Prefab")]
+	public static void ShowWindow()
+	{
+		// Get existing open window or if none, make a new one.
+		var window = GetWindow<ReplaceTool>();
+
+		// Open / Show window.
+		window.Show();
+	}
+
+	private void OnGUI()
+	{
+		 // Check to have data.
+        InitDataIfNeeded();
+        // Window title.
+        EditorGUILayout.LabelField("Replace Tool", EditorStyles.boldLabel);
+        // ReplaceObject field. This object will be used to replace selected game objects.
+        EditorGUILayout.PropertyField(replaceObjectField);
+        // Space.
+        EditorGUILayout.Separator();
+        // Title for section with objects to replace.
+        EditorGUILayout.LabelField("Selected objects to replace", EditorStyles.boldLabel);
+        // Space.
+        EditorGUILayout.Separator();
+        // Saving number of objects to replace.
+        int objectToReplaceCount = data.objectsToReplace != null ? data.objectsToReplace.Length : 0;
+        EditorGUILayout.IntField("Object count", objectToReplaceCount);
+        // Adding a little indentation.
+        EditorGUI.indentLevel++;
+        // Printing information when no object is selected on scene.
+        if (objectToReplaceCount == 0)
+        {
+            EditorGUILayout.Separator();
+            EditorGUILayout.LabelField("Select object o objects in hierarchy to replace them", EditorStyles.wordWrappedLabel);
+        }
+        // Scroll view with selected game objects.
+        selectObjectScrollPosition = EditorGUILayout.BeginScrollView(selectObjectScrollPosition);
+        // Read only list of objects to replace
+        GUI.enabled = false;
+        if (data && data.objectsToReplace != null)
+        {
+            foreach (var go in data.objectsToReplace)
+            {
+                EditorGUILayout.ObjectField(go, typeof(GameObject), true);
+            }
+        }
+        GUI.enabled = true;
+        // Closing scroll view.
+        EditorGUILayout.EndScrollView();
+        // Removing indentation for rest of the window.
+        EditorGUI.indentLevel--;
+        // Space.
+        EditorGUILayout.Separator();
+        // Replace button.
+        if (GUILayout.Button("Replace"))
+        {
+	        // Check if replace object is assigned.
+	        if (!replaceObjectField.objectReferenceValue)
+	        {
+		        Debug.LogErrorFormat("[Replace Tool] {0}", "Missing prefab to replace with!");
+		        return;
+	        }
+	        // Check if there are objects to replace.
+	        if (data.objectsToReplace.Length == 0)
+	        {
+		        Debug.LogErrorFormat("[Replace Tool] {0}", "Missing objects to replace!");
+		        return;
+	        }
+	        ReplaceSelectedObjects(data.objectsToReplace, data.replaceObject);
+
+        }
+        // Space.
+        EditorGUILayout.Separator();
+        // Applying any changes on data.
+        serializedData.ApplyModifiedProperties();
+
+	}
+	private void OnInspectorUpdate()
+	{
+		// If data was changed, force repaint.
+		if (serializedData != null && serializedData.UpdateIfRequiredOrScript())
+		{
+			this.Repaint();
+		}
+	}
+	private void OnSelectionChange()
+	{
+		// Check to have data.
+		InitDataIfNeeded();
+		// Creating filter to gather object only on scene.
+		SelectionMode objectFilter = SelectionMode.Unfiltered ^ ~(SelectionMode.Assets | SelectionMode.DeepAssets | SelectionMode.Deep);
+		Transform[] selection = Selection.GetTransforms(objectFilter);
+		// Converting Transform array into GameObject array.
+		data.objectsToReplace = selection.Select(s => s.gameObject).ToArray();
+		// Force repaint as update is needed.
+		if (serializedData.UpdateIfRequiredOrScript())
+		{
+			this.Repaint();
+		}
+	}
+
+	/// <summary>
+	/// Replaces game objects with provided replace object.
+	/// </summary>
+	/// <param name="objectToReplace">Game Objects to replace.</param>
+	/// <param name="replaceObject">Replace object.</param>
+	private void ReplaceSelectedObjects(GameObject[] objectToReplace, GameObject replaceObject)
+	{
+		Debug.Log("[Replace Tool] Replace process");
+		// Loop through object to replace.
+		for (int i = 0; i < objectToReplace.Length; i++)
+		{
+			var go = objectToReplace[i];
+			// Register current game object to Undo action in editor.
+			Undo.RegisterCompleteObjectUndo(go, "Saving game object state");
+			// Creating replace object as the same position and same parent.
+			var inst = Instantiate(replaceObject, go.transform.position, go.transform.rotation, go.transform.parent);
+			inst.transform.localScale = go.transform.localScale;
+			// Register object creation for Undo action in editor.
+			Undo.RegisterCreatedObjectUndo(inst, "Replacement creation.");
+			// Changing parent for all children of current game object.
+			foreach (Transform child in go.transform)
+			{
+				// Saving action for Undo action in editor.
+				Undo.SetTransformParent(child, inst.transform, "Parent Change");
+			}
+			// Destroying current game object with save for Undo action in editor.
+			Undo.DestroyObjectImmediate(go);
+		}
+		Debug.LogFormat("[Replace Tool] {0} objects replaced on scene with {1}", objectToReplace.Length, replaceObject.name);
+	}
+}