Added InitOnlyAttribute

InitOnlyAttribute adds a helpbox in the inspector during play mode to indicate that the field with the attribute is only used for initialization, and thus will only affect new instances, or after re-entering play mode.

UOP1_Project/Assets/Scripts/StateMachine/Editor/Utilities/InitOnlyAttributeDrawer.cs

+using UnityEditor;
+using UnityEngine;
+
+namespace UOP1.StateMachine.Editor
+{
+	[CustomPropertyDrawer(typeof(InitOnlyAttribute))]
+	public class InitOnlyAttributeDrawer : PropertyDrawer
+	{
+		private static readonly string _text = "Changes to this field will only take effect on new state machine instances, or the next time you enter play mode.";
+		private static readonly GUIStyle _style = new GUIStyle(GUI.skin.GetStyle("helpbox")) { padding = new RectOffset(5, 5, 5, 5) };
+
+		public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
+		{
+			if (EditorApplication.isPlaying)
+			{
+				position.height = _style.CalcHeight(new GUIContent(_text), EditorGUIUtility.currentViewWidth);
+				EditorGUI.HelpBox(position, _text, MessageType.Info);
+				position.y += position.height + EditorGUIUtility.standardVerticalSpacing;
+				position.height = EditorGUI.GetPropertyHeight(property, label);
+			}
+
+			EditorGUI.PropertyField(position, property, label);
+		}
+
+		public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
+		{
+			float height = EditorGUI.GetPropertyHeight(property, label);
+
+			if (EditorApplication.isPlaying)
+			{
+				height += _style.CalcHeight(new GUIContent(_text), EditorGUIUtility.currentViewWidth)
+					+ EditorGUIUtility.standardVerticalSpacing;
+			}
+
+			return height;
+		}
+	}
+}

UOP1_Project/Assets/Scripts/StateMachine/Editor/Utilities/InitOnlyAttributeDrawer.cs.meta

+fileFormatVersion: 2
+guid: b95d43eb2b350bb4daea0ec542dbff60
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

UOP1_Project/Assets/Scripts/StateMachine/Utilities.meta

+fileFormatVersion: 2
+guid: fbce2081495798d40b0abeac468abcd6
+folderAsset: yes
+DefaultImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

UOP1_Project/Assets/Scripts/StateMachine/Utilities/InitOnlyAttribute.cs

+using System;
+using UnityEngine;
+
+namespace UOP1.StateMachine
+{
+	[AttributeUsage(AttributeTargets.Field)]
+	public class InitOnlyAttribute : PropertyAttribute { }
+}

UOP1_Project/Assets/Scripts/StateMachine/Utilities/InitOnlyAttribute.cs.meta

+fileFormatVersion: 2
+guid: c46c099afcb2c684a9253941297b4eb9
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: