Minor refactor changes; implement NotPrefabObjectOnlyAttribute & Drawer

Author: arimger

Assets/Editor Toolbox/Editor/Drawers/Regular/NotNullAttributeDrawer.cs

@@ -41,16 +41,13 @@ protected override void OnGUISafe(Rect position, SerializedProperty property, GU
             }
         }
 
-
         public override bool IsPropertyValid(SerializedProperty property)
         {
             return property.propertyType == SerializedPropertyType.ObjectReference;
         }
 
-
         private NotNullAttribute Attribute => attribute as NotNullAttribute;
 
-
         private static class Style
         {
 #if UNITY_2019_3_OR_NEWER

Assets/Editor Toolbox/Editor/Drawers/Regular/NotPrefabObjectOnlyAttributeDrawer.cs

@@ -0,0 +1,38 @@
+using UnityEditor;
+using UnityEngine;
+
+namespace Toolbox.Editor.Drawers
+{
+    [CustomPropertyDrawer(typeof(NotPrefabObjectOnlyAttribute))]
+    public class NotPrefabObjectOnlyAttributeDrawer : ObjectValidationDrawer
+    {
+        protected override string GetWarningMessage()
+        {
+            return "Assigned object can't be a Prefab.";
+        }
+
+        protected override bool IsObjectValid(Object objectValue, SerializedProperty property)
+        {
+            if (objectValue == null)
+            {
+                return false;
+            }
+
+            var attribute = Attribute;
+            if (PrefabUtility.GetPrefabAssetType(objectValue) == PrefabAssetType.NotAPrefab)
+            {
+                return true;
+            }
+
+            if (PrefabUtility.GetPrefabInstanceStatus(objectValue) == PrefabInstanceStatus.Connected &&
+                attribute.AllowInstancedPrefabs)
+            {
+                return true;
+            }
+
+            return false;
+        }
+
+        private NotPrefabObjectOnlyAttribute Attribute => attribute as NotPrefabObjectOnlyAttribute;
+    }
+}

Assets/Editor Toolbox/Editor/Drawers/Regular/NotPrefabObjectOnlyAttributeDrawer.cs.meta

@@ -34,7 +34,6 @@ protected virtual string GetWarningMessage()
 
         protected abstract bool IsObjectValid(Object objectValue, SerializedProperty property);
 
-
         public override bool IsPropertyValid(SerializedProperty property)
         {
             return property.propertyType == SerializedPropertyType.ObjectReference;

Assets/Editor Toolbox/Editor/Drawers/Regular/ObjectValidationDrawer.cs

@@ -63,7 +63,6 @@ private void HandleTargetPicker(Rect position, SerializedProperty property)
             }
         }
 
-
         protected override float GetPropertyHeightSafe(SerializedProperty property, GUIContent label)
         {
             return SceneExists(property.stringValue)
@@ -88,13 +87,11 @@ protected override void OnGUISafe(Rect position, SerializedProperty property, GU
             HandleTargetPicker(position, property);
         }
 
-
         public override bool IsPropertyValid(SerializedProperty property)
         {
             return property.propertyType == SerializedPropertyType.String;
         }
 
-
         private static class Style
         {
             internal static readonly float rowHeight = EditorGUIUtility.singleLineHeight;

Assets/Editor Toolbox/Editor/Drawers/Regular/SceneNameAttributeDrawer.cs

@@ -19,7 +19,6 @@ private GameObject GetGameObject(Object reference)
             return null;
         }
 
-
         protected override string GetWarningMessage()
         {
             return "Assigned object has to be instantiated in the Scene.";
@@ -28,7 +27,7 @@ protected override string GetWarningMessage()
         protected override bool IsObjectValid(Object objectValue, SerializedProperty property)
         {
             var gameObject = GetGameObject(objectValue);
-            return gameObject && !string.IsNullOrEmpty(gameObject.scene.name);
+            return gameObject != null && !string.IsNullOrEmpty(gameObject.scene.name);
         }
     }
 }

Assets/Editor Toolbox/Editor/Drawers/Regular/SceneObjectOnlyAttributeDrawer.cs

@@ -34,7 +34,6 @@ protected override void OnGUISafe(Rect position, SerializedProperty property, GU
             EditorGUI.EndProperty();
         }
 
-
         public override bool IsPropertyValid(SerializedProperty property)
         {
             return property.propertyType == SerializedPropertyType.Enum;

Assets/Editor Toolbox/Editor/Drawers/Regular/SearchableEnumAttributeDrawer.cs

@@ -251,6 +251,10 @@ Supported types: **GameObject, Component**.
 
 Supported types: **GameObject, Component**.
 
+#### NotPrefabObjectOnlyAttribute
+
+Supported types: **GameObject, Component**.
+
 #### LeftToggleAttribute
 
 Supported types: **bool**.

Assets/Editor Toolbox/README.md

@@ -0,0 +1,17 @@
+using System;
+using System.Diagnostics;
+
+namespace UnityEngine
+{
+    /// <summary>
+    /// Validates input values and accepts only objects that are not Prefabs.
+    /// 
+    /// <para>Supported types: <see cref="GameObject"/> and any <see cref="Component"/>.</para>
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Field, AllowMultiple = false, Inherited = true)]
+    [Conditional("UNITY_EDITOR")]
+    public class NotPrefabObjectOnlyAttribute : PropertyAttribute
+    {
+        public bool AllowInstancedPrefabs { get; set; }
+    }
+}