When subscribing to delegates and events in Unity/C#, publishers hold strong references to subscriber instances, so even after unsubscribing the GC cannot collect them, and "ghost callbacks" plus memory leaks often occur--e.g. callbacks still firing after scene changes or object destruction.

This package wraps delegates, Action, and events in weak references, so when the target is collected by the GC (plain C# objects) or destroyed in Unity (UnityEngine.Object), it is automatically treated as "dead."

What it does

• Reduces memory leaks: If you forget to unsubscribe, references disappear once the target instance is gone, so it becomes eligible for GC.
• Prevents ghost callbacks: No invocations on destroyed Unity objects or already-collected instances.
• Unity-aware: UnityEngine.Object is considered "dead" at Destroy() time (via UnityWeakReference, respecting Unity null semantics).

Provided types: UnityWeakReference, WeakDelegate, WeakAction/WeakAction, WeakEvent/WeakEvent, WeakEventSource. See the Type Summary and sections below for details.

• No lambdas or anonymous methods: Weak references track only the delegate target instance. Lambdas and anonymous methods target compiler-generated closures, not the intended "subscriber" instance. Use method groups or named methods only.
  • e.g. Subscribe(handler.OnRaise) / Subscribe(() => handler.OnRaise())
• Not thread-safe: WeakEvent, WeakEventSource, etc. do not assume concurrent multi-threaded access. Synchronize subscribe/unsubscribe/raise from other threads at the call site.
• Unity-only type: UnityWeakReference supports only T : UnityEngine.Object. For plain C# objects use .NET WeakReference or this package's WeakDelegate/WeakAction.
• Cleanup on Raise: In WeakEvent/WeakEventSource, "dead" subscribers are removed from the list when Raise is called. If Raise is infrequent, dead references may remain until then.

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A weak-reference wrapper for Unity's UnityEngine.Object.
It extends System.WeakReference but respects Unity's special null semantics so that IsAlive and the target are evaluated correctly.

• Plain WeakReference: Once the target is collected by the GC, Target becomes null and IsAlive is false.
• Unity objects: UnityEngine.Object can be in a "destroyed" state (fake null) even when the C# reference exists, so null checks must use Unity's overloaded == null behavior.
• UnityWeakReference: It casts Target to T (a Unity object) and checks that result with Unity's null semantics, then exposes IsAlive and TryGetTarget accordingly.

Basic usage (TryGetTarget)

Invalidation after Destroy

• Role: Holds only the delegate target weakly. When the target is GC'd (plain) or destroyed (Unity object), TryGetDelegate() returns null.
• Restriction: Lambda and anonymous methods are not allowed. Use method groups or named delegates only.
• Unity: When the target is a UnityEngine.Object, uses UnityWeakReference internally so destroyed objects are treated as dead (#if UNITY_2017_1_OR_NEWER).

Members

• IsAlive: true if the method is static or the target is alive.
• TryGetDelegate(): Returns the delegate when alive, null otherwise.

• Role: Holds an Action or Action weakly. Invoke() runs only when the target is alive; otherwise no-op.
• Restriction: Lambda and anonymous methods are not allowed. Uses WeakDelegate internally.
• Overloads: No-arg WeakAction, one-arg WeakAction ... up to WeakAction.

Members: IsAlive, Invoke() / Invoke(arg1, ...) (up to 10 args).

• Role: Subscribe, unsubscribe, and raise multiple Action handlers with weak references. Dead references are removed on Raise.
• Restriction: Lambda and anonymous methods are not allowed. Not thread-safe (same thread or caller synchronization required).
• Overloads: No-arg WeakEvent, one-arg WeakEvent ... up to WeakEvent.

Members: Subscribe, Unsubscribe, Raise / Raise(arg1, ...), + / - operators.

• Role: Weak event following the EventHandler pattern. Passes sender and TEventArgs.
• Restriction: Lambda and anonymous methods are not allowed. Not thread-safe.

Members: Subscribe, Unsubscribe, Raise(object sender, TEventArgs args), + / - operators.

• Changelog: CHANGELOG
• License: LICENSE
• Author: xpTURN