Apologies for reviving a thread that’s over a year old, but since the issue wasn’t fully resolved and hasn’t been addressed in this manner before, I wanted to share a solution for those who might still be encountering this problem or stumble upon this post in search of answers.
The persistent event subscriptions, despite efforts to unsubscribe, particularly in the context of Unity’s scene management and C#'s handling of lambda expressions for event subscription and unsubscription, are due to lambda expressions creating a new delegate instance each time they are used. Therefore, attempting to unsubscribe using a lambda expression does not match the delegate instance you originally subscribed with, leaving the original subscription active.
To resolve this, it’s essential to use a consistent delegate instance for both subscribing and unsubscribing from events. This consistency can be achieved by either defining methods directly or using actions as intermediary variables. Here’s how you can adjust your code to ensure proper subscription management and why you should use OnEnable() and OnDisable() for this purpose:
Avoid subscribing with lambda expressions like this:
private void Awake()
{
playerControls.Combat.Reload.performed += context => Reload();
}
private void Reload()
{
// Reload code here
}
Instead, subscribe by directly referencing a method in OnEnable() and unsubscribe in OnDisable():
private void OnEnable()
{
playerControls.Combat.Reload.performed += Reload;
}
private void OnDisable()
{
playerControls.Combat.Reload.performed -= Reload;
}
private void Reload(InputAction.CallbackContext context)
{
// Reload code here
}
Using OnEnable() for subscriptions and OnDisable() for unsubscriptions is crucial because Awake() is only called when the script instance is loaded, which doesn’t account for objects being enabled or disabled throughout the scene’s lifecycle. OnEnable() is called every time the object becomes active in the scene, making it the ideal place to set up event subscriptions. Similarly, OnDisable() is called when the object becomes inactive, allowing you to clean up subscriptions and prevent actions from being triggered when they shouldn’t be, such as after an object is destroyed or a scene is unloaded.
This approach ensures your event handlers are correctly managed, avoiding issues such as duplicate event firing and enhancing the robustness of your event handling logic, especially in complex Unity projects with multiple scene loads and object state changes.