Saving custom inspector references

Continuing my tradition of answering my own questions, here's the answer. The variables must be serialised. What had confused me was several forum threads that claimed serialization didn't work when unity was restarted, this is not true. To help my fellow n00b's here are two scripts that will serialise string, int, float and gameobjects. For some reason I'm getting a warning that ObjectField is no longer supported. I've used the new system of "Allow Scene Objects", implemented in the code below, but I'm still getting this warning. Is this just unity having a bit of a weird turn over the changing systems or have I done something wrong? Either way the code compiles and runs with no real problems.

The first script should be dragged onto your object in the inspector.

SerializeTest.cs

 using UnityEngine;
 
 [System.Serializable]
 
 public class SerializeTest : MonoBehaviour 
 {
     [SerializeField]
     public string TestString=" ";
     
     [SerializeField]
     public int TestInt=0;
     
     [SerializeField]
     public float TestFloat=0f;
     
     [SerializeField]
     public GameObject TestObject=null;
 }

The second script should be put into a folder called "Editor".

SerializeTestEditor.cs

 using UnityEditor;
 using UnityEngine;
 
 [CustomEditor(typeof(SerializeTest))]
 
 public class SerializeTestEditor : Editor {
     
     bool allowSceneObjects;
     
     public override void OnInspectorGUI() 
     {
         SerializeTest TargetScript = target as SerializeTest;
         
         GUILayout.Label("Serialize test");
         EditorGUILayout.Separator();
          
         GUILayout.BeginHorizontal();
             GUILayout.Label("String");
             TargetScript.TestString = EditorGUILayout.TextField(TargetScript.TestString);
         GUILayout.EndHorizontal();
         
         GUILayout.BeginHorizontal();
             GUILayout.Label("Int");
             TargetScript.TestInt = EditorGUILayout.IntField(TargetScript.TestInt);
         GUILayout.EndHorizontal();
         
         GUILayout.BeginHorizontal();
             GUILayout.Label("Float");
             TargetScript.TestFloat = EditorGUILayout.FloatField(TargetScript.TestFloat);
         GUILayout.EndHorizontal();
         
         GUILayout.BeginHorizontal();
             GUILayout.Label("Object");
             allowSceneObjects = !EditorUtility.IsPersistent(target);
             TargetScript.TestObject = EditorGUILayout.ObjectField(TargetScript.TestObject, typeof(GameObject), allowSceneObjects) as GameObject;
         GUILayout.EndHorizontal();        
     }
 }