[WIKI] Prevent Reset() to nullify objects like Unity does

This is my attempt to mimic the behavior in Unity such that when you do reset in-house components such as MeshFilter, the mesh reference is kept, very handy when you wish to reset only a subset of your properties!

Code (CSharp):

1. #if UNITY_EDITOR
2. using System;
3. using System.Linq.Expressions;
4. using System.Reflection;
5. using JetBrains.Annotations;
6. using UnityEditor;
7. using Object = UnityEngine.Object;
8.  
9. namespace Z
10. {
11.     /// <summary>
12.     ///     Stores objects references in registry.
13.     /// </summary>
14.     public static class EditorPreferences
15.     {
16.         private static void Load<TSource, TProperty>(
17.             [NotNull] TSource source, [NotNull] string sourceKey, [CanBeNull] ref TProperty target, [NotNull] string targetKey)
18.             where TSource : Object
19.             where TProperty : Object
20.         {
21.             if (source == null)
22.                 throw new ArgumentNullException(nameof(source));
23.  
24.             if (sourceKey == null)
25.                 throw new ArgumentNullException(nameof(sourceKey));
26.  
27.             if (targetKey == null)
28.                 throw new ArgumentNullException(nameof(targetKey));
29.  
30.             var sourceId = source.GetInstanceID();
31.  
32.             var key = $"{sourceKey}.{sourceId}.{targetKey}";
33.  
34.             if (!EditorPrefs.HasKey(key))
35.                 return;
36.  
37.             var id = EditorPrefs.GetInt(key);
38.  
39.             var o = EditorUtility.InstanceIDToObject(id);
40.             if (o == null)
41.                 return;
42.  
43.             target = o as TProperty;
44.         }
45.  
46.         public static void Load<TSource, TProperty>([NotNull] TSource source, [NotNull] Expression<Func<TSource, TProperty>> property)
47.             where TSource : Object
48.             where TProperty : Object
49.         {
50.             if (source == null)
51.                 throw new ArgumentNullException(nameof(source));
52.  
53.             if (property == null)
54.                 throw new ArgumentNullException(nameof(property));
55.  
56.             if (!(property.Body is MemberExpression memberExpression))
57.                 throw new ArgumentNullException(nameof(memberExpression));
58.  
59.             var fieldInfo = memberExpression.Member as FieldInfo;
60.             if (fieldInfo == null)
61.                 throw new ArgumentNullException(nameof(fieldInfo));
62.  
63.             var sourceKey = source.GetType().Name;
64.  
65.             var targetKey = fieldInfo.Name;
66.  
67.             var target = default(TProperty);
68.  
69.             Load(source, sourceKey, ref target, targetKey);
70.  
71.             fieldInfo.SetValue(source, target);
72.         }
73.  
74.         private static void Save<TSource, TProperty>(
75.             [NotNull] TSource source, [NotNull] string sourceKey, [CanBeNull] TProperty target, [NotNull] string targetKey)
76.             where TSource : Object
77.             where TProperty : Object
78.         {
79.             if (source == null)
80.                 throw new ArgumentNullException(nameof(source));
81.  
82.             if (sourceKey == null)
83.                 throw new ArgumentNullException(nameof(sourceKey));
84.  
85.             if (target == null)
86.                 return;
87.  
88.             if (targetKey == null)
89.                 throw new ArgumentNullException(nameof(targetKey));
90.  
91.             var sourceId = source.GetInstanceID();
92.             var targetId = target.GetInstanceID();
93.  
94.             EditorPrefs.SetInt($"{sourceKey}.{sourceId}.{targetKey}", targetId);
95.         }
96.  
97.         public static void Save<TSource, TProperty>([NotNull] TSource source, [NotNull] Expression<Func<TSource, TProperty>> property)
98.             where TSource : Object
99.             where TProperty : Object
100.         {
101.             if (source == null)
102.                 throw new ArgumentNullException(nameof(source));
103.  
104.             if (property == null)
105.                 throw new ArgumentNullException(nameof(property));
106.  
107.             if (!(property.Body is MemberExpression memberExpression))
108.                 throw new ArgumentNullException(nameof(memberExpression));
109.  
110.             var info = memberExpression.Member as FieldInfo;
111.             if (info == null)
112.                 throw new ArgumentNullException(nameof(info));
113.  
114.             var sourceKey = source.GetType().Name;
115.  
116.             var target = info.GetValue(source) as Object;
117.             if (target == null)
118.                 return;
119.  
120.             var targetKey = info.Name;
121.  
122.             Save(source, sourceKey, target, targetKey);
123.         }
124.     }
125. }
126. #endif

Use it like this:

Code (CSharp):

1.     public ScrollRect ScrollView;
2.  
3.     private void OnValidate()
4.     {
5.         EditorPreferences.Save(this, s => s.ScrollView);
6.     }
7.  
8.     private void Reset()
9.     {
10.         EditorPreferences.Load(this, s => s.ScrollView);
11.     }
12.  

Now when you reset the ScrollView reference is kept, works rather well .

Sharing this with the community, improvements are welcome!