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Don't retain observers added to NSNotificationCenter

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Marmalade SDK, in its video player code, expects the added observer to be deallocated after releasing itself, without removing the observer first.
This can only happen if the NSNotificationCenter doesn't also retain the observer.

Change-Id: I072ce1400730b550c74921c0bcd3b8c92f376042
This commit is contained in:
alborrajo
2026-01-10 13:09:43 +01:00
parent d2d2c4ff72
commit 99a7b8a966
1 changed files with 18 additions and 4 deletions
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22
src/frameworks/foundation/ns_notification_center.rs
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@@ -59,7 +59,6 @@ pub const CLASSES: ClassExports = objc_classes! {
let host_obj = env.objc.borrow_mut::<NSNotificationCenterHostObject>(this);
let observers = std::mem::take(&mut host_obj.observers);
for observer in observers.values().flatten() {
release(env, observer.observer);
release(env, observer.object);
}
env.objc.dealloc_object(this, &mut env.mem);
@@ -90,8 +89,24 @@ pub const CLASSES: ClassExports = objc_classes! {
object,
);
retain(env, observer);
retain(env, object); // TODO: is it correct that this is retained?
// When adding an observer, only the object is retained so it doesn't get
// deallocated before the notification is delivered. Some apps, such as
// Dungeon Hunter 2, rely on this being the case.
// The observer is not retained to avoid retain cycles.
// https://stackoverflow.com/a/36582937
// While not explicitly stated by the documentation, there's a paragraph
// that hints at this behavior:
// "If your app targets iOS 9.0 and later or macOS 10.11 and later, you do
// not need to unregister an observer that you created with this function.
// If you forget or are unable to remove an observer, the system cleans up
// the next time it would have posted to it."
// https://developer.apple.com/documentation/foundation/notificationcenter/addobserver(_:selector:name:object:)?language=objc
// Implying that prior to these versions, it's unsafe to not remove an
// observer. It's been observed that some apps expect and rely on this
// behavior, such as Marmalade SDK games that use the Movie Player
// (Pandemonium and COD Zombies, for example).
retain(env, object);
let host_obj = env.objc.borrow_mut::<NSNotificationCenterHostObject>(this);
host_obj.observers.entry(name).or_default().push(Observer {
@@ -142,7 +157,6 @@ pub const CLASSES: ClassExports = objc_classes! {
};
for removed_observer in removed_observers {
release(env, removed_observer.observer);
release(env, removed_observer.object);
}
}