Auto Singleton — Public API

SingletonAttribute

Attribute

Decorate a MonoBehaviour or ScriptableObject class with this attribute to register it as an automatically managed singleton. The editor will create and maintain the asset or prefab, and the runtime will instantiate it at startup.

Public Fields

string displayName	Name given to this singleton in the Assets folder.
string folderPath	Where to create the asset or prefab, relative to the Assets folder. When `inherited` is true, derived classes are also created here.
bool inherited	When true, the attribute also applies to classes derived from the decorated type.

Singleton

static class

Utility to manually add and remove singleton instances at runtime. Use this when you need to register objects that are not covered by SingletonAttribute and any reference type is accepted. All methods require play mode.

Adding a MonoBehaviour via Add does not reparent it under the Auto Singleton root GameObject, so it will be destroyed on scene load unless you call Object.DontDestroyOnLoad on it yourself.

Static Methods: Add

void Add<T>(T singleton) where T : class	Register a singleton instance. Throws `ArgumentException` if an instance of the same exact type is already registered.
void Add<T>(IEnumerable<T> singletons) where T : class	Register multiple singleton instances. Throws `ArgumentNullException` if the collection is null.
void Add<T>(params T[] singletons) where T : class	Register multiple singleton instances via params.

Static Methods: Remove

Only instances that were manually added via Add can be removed. Automatically managed singletons cannot be removed at runtime.

void Remove<T>(T singleton) where T : class	Unregister a singleton instance. Throws `ArgumentException` if the instance is not registered or was not added manually.
void Remove<T>(IEnumerable<T> singletons) where T : class	Unregister multiple singleton instances. Throws `ArgumentNullException` if the collection is null.
void Remove<T>(params T[] singletons) where T : class	Unregister multiple singleton instances via params.

Singleton<T>

static class

Generic access class for singleton instances. T can be a concrete type, a base class, or an interface. Instances returns every registered object assignable to T, while Instance returns the one selected by a SelectInstance call (or the only one if there is exactly one registered instance of exact type T). All members require play mode; in the editor, accessing them outside play mode throws InvalidOperationException.

Constraint: T : class.

Static Properties

T Instance	The selected singleton instance. In the editor, throws `InvalidOperationException` if no instance is registered or if multiple are registered and none was selected via `SelectInstance`. Returns `null` in builds when no instance is available.
IReadOnlyList<T> Instances	All registered singleton instances assignable to `T`, regardless of which one is selected.
bool HasInstance	True if `Instance` has a value. Use this to check before accessing `Instance` to avoid an exception.

Static Methods: Access

bool TryGetInstance(out T instance)	Non-throwing alternative to `Instance`. Sets `instance` to the selected singleton and returns true; sets it to `null` and returns false if none is selected.
T[] Find(Predicate<T> predicate)	Return a new array of all registered instances that match the predicate. Returns an empty array if none match.

Static Methods: SelectInstance

All SelectInstance overloads set Instance to a chosen entry from Instances and return true on success. On failure they leave Instance unchanged, log a warning in the editor, and return false.

bool SelectInstance(Predicate<T> predicate)	Select the unique instance matching the predicate. Fails if zero or more than one instance matches.
bool SelectInstance(Func<T, int> priority)	Select the instance with the highest int priority score. Fails if multiple instances share the top score.
bool SelectInstance(Func<T, float> priority)	Select the instance with the highest float priority score. Fails if multiple instances share the top score.
bool SelectInstance(T instance)	Select the given instance directly. Fails if it is not in the registered collection.
bool SelectInstance<SubT>() where SubT : T	Select the registered instance whose exact runtime type is `SubT`. Fails if none is found.
bool SelectInstance()	Select the sole registered instance derived from `T`. Fails if there are zero or more than one.