SerializeReference Selector

Pick an implementation right in the Inspector — from a searchable list, without a custom editor.

Quick start

Before — Unity API	After — FastTools
[SerializeReference] private IWeapon _primary = new Pistol();	[TypeSelector] [SerializeReference] private IWeapon _primary;

Which classes are offered

The list follows the field type; the attribute can narrow it with extra types.

public interface IMelee : IWeapon { }
public sealed class Sword : IMelee { }

public abstract class StatusEffect { }

public class Modifier<T> : IModifier { }
public sealed class DamageModifier : Modifier<float> { }

Field type	What is listed
Interface IWeapon	Classes that implement it: Crossbow, Pistol, Railgun, Shotgun, Sword
IWeapon and typeof(IMelee) in the attribute	Classes that fit both: Sword
Abstract class StatusEffect	Its subclasses: BurnEffect, FreezeEffect
Modifier<float>	The subclass DamageModifier and Modifier<Single> itself
List<IModifier>	AmmoModifier, DamageModifier, NameModifier and Modifier<T> with a choice of T

• In the Inspector of a runtime object, classes from editor-only assemblies (UnityEditor, Editor-only asmdefs, Editor folders) are left out: a player build cannot create them.
• Generic arguments are inferred from the field type; when they cannot be, the window asks for each one and offers only types Unity can serialize.
• A constraint can also come from another field.
• [TypeSelectorDisplay] sets a class's row in the list or hides the class.

Required field

[TypeSelector(Required = true)]
[SerializeReference] private IWeapon _primary;

With Required = true, an empty field shows Required reference is not set; see Required field.

Lists

In a list with [TypeSelector], “+” opens the class picker and adds a new instance, and <None> adds an empty element. With several objects selected, each gets its own instance, all in one Undo group.

Switching the class

The new instance receives the values of fields with the same names:

Field	Pistol	→ Shotgun
Damage	37	37
Magazine Size	12	—
Pellets	—	8, the initial value

note

A nested reference with the same name moves to the new class as the same instance, not a copy.

A .cs script dragged from Project onto the field header switches the field to its class the same way.

Header menu

Right-click the field header:

Item	What it does
Copy Serialize Reference	Copies the field's class and data; the copy lasts until the next domain reload
Paste Serialize Reference	Pastes the copy into a field of a compatible type; a copied empty field clears it
Make Unique Reference	Gives the field its own copy of a shared reference; not shown on an unshared one
Find Usages of Pistol	Searches the project for the class through Unity Search
Link to Existing → …	Points the field at the instance of another field on the same object
Create New Script…	Creates a [Serializable] class for the field type and assigns it after compilation
Save as Template…	Saves the value under a name; templates live in the editor settings on this machine, not in the project
Paste Template → …	Creates an instance from a template; only templates that fit the field are listed
Paste Template → Remove Missing (N)…	Deletes templates whose class does not load; shown only when there are any

warning

Copy/Paste and templates do not carry nested [SerializeReference] fields: a copied Railgun pastes without its _chargeEffect.

Shared references

Two fields of an object can point at one instance: an edit through one shows in the other. Such fields are marked Shared reference #N, and Make unique gives the field its own copy, nested references included.

A duplicated list element gets its own instance instead of a reference to the same one. The Auto de-alias duplicated list elements setting in the shared settings controls this and is on by default.

Repairing missing types

After a class is renamed, moved or deleted, the field shows Missing type, while the data stays in the asset.

Action	What it does
Fix	Opens the class picker, including classes hidden with Hidden
→ Pistol	Assigns the suggested class; the tooltip gives the reason: the same name, the same name in another case, or a similar name

warning

On an asset, Fix rewrites the file, and Undo does not revert it.

In a scene or Prefab Mode the repair stays in memory: Undo reverts it, and saving makes it final and clears the object's Undo history. Such a repair brings back only flat top-level fields: nested objects, arrays, lists, vectors, colours and object references get their default values.

When there is no Fix

Case	What to do
Several objects selected	Select one: until then Missing type is not shown
Unsaved changes in the scene or Prefab Mode	Save: until then the field shows <None> without Missing type
Prefab instance, class stored in the source prefab	Repair the source prefab; the tooltip names it
Prefab instance, class set through an override	Choose a new class on the instance or revert the override

SerializeReference Tooling repairs everything else.

Custom inspector

In your own editor, a regular PropertyField draws a [TypeSelector] field: the class picker and the list's “+” come by themselves, with no package call.

UI Toolkit — CreateInspectorGUI	IMGUI — OnInspectorGUI
new PropertyField( serializedObject .FindProperty("_sidearms"))	EditorGUILayout.PropertyField( serializedObject .FindProperty("_sidearms"));

If a [SerializeReference] field has no [TypeSelector] attribute, or a list element is drawn on its own through GetArrayElementAtIndex, PropertyField shows no class picker. Your own editor can draw it by calling one of these methods:

Method	Draws
SerializeReferenceEditorGUI.CreateField()	A field in CreateInspectorGUI
SerializeReferenceEditorGUI.CreateList()	A list in CreateInspectorGUI
SerializeReferenceEditorGUI.DrawFieldLayout()	A field in OnInspectorGUI
SerializeReferenceIMGUIList.Draw()	A list in OnInspectorGUI

Constraints on top of the field type go in the baseTypes argument, like the types in [TypeSelector(...)].

Limitations

• Allow. Has no effect on [SerializeReference] — analyzer AFT0002 reports it.
• Incompatible constraints. When no class fits both the field type and all the attribute's types, the class list is empty — for example, [TypeSelector(typeof(Sword))] on StatusEffect _onHit;. Analyzers AFT0003, AFT0005 and AFT0009 report it at compile time.

Package sample

The Loadout fields from this page and assets with missing types to try Fix on are in the SerializeReferences sample.