public static void NotifyWhenDeallocated(NSObject obj, Action deallocated)
{
// Add an associated object which will be 'released'd when the obj
// to watch is deallocated. When 'release' is sent, then invoke
// the 'deallocated' callback.
var notifier = new ReleaseNotifier(deallocated);
obj.SetAssociatedObject(IntPtr.Zero, notifier, AssociatedObjects.AssociationPolicy.Retain);
notifier.Dispose(); // remove any managed references.
notifier.enabled = true; // notify on the next 'release' message.
}
public bool UsableUntilDeadImpl()
{
// This test ensure that the main thread can send messages to a garbage collected object,
// until the final 'release' message for the managed reference has been sent
// (on the main thread).
var notifierHandle = IntPtr.Zero;
// bool isDeallocated = false;
Action deallocated = () => {
//Console.WriteLine ("Final release!");
// isDeallocated = true;
};
ManualResetEvent isCollected = new ManualResetEvent(false);
Action collected = () => {
//Console.WriteLine ("Garbage collected!");
isCollected.Set();
};
bool isNotified = false;
Action notified = () => {
//Console.WriteLine ("Notified");
isNotified = true;
};
// Create an object whose handle we store in a local variable. We do not
// store the object itself, since we want the object to be garbage collected.
var t = new Thread(() => {
var obj = new Notifier(collected, notified);
ReleaseNotifier.NotifyWhenDeallocated(obj, deallocated);
notifierHandle = obj.Handle;
})
{
IsBackground = true,
};
t.Start();
t.Join();
// Now we have a handle to an object that may be garbage collected at any time.
int counter = 0;
do
{
GC.Collect();
GC.WaitForPendingFinalizers();
} while (counter++ < 10 && !isCollected.WaitOne(10));
// Now we have a handle to a garbage collected object.
if (!isCollected.WaitOne(0))
{
// Objects may randomly not end up collected (at least in Boehm), because
// other objects may happen to contain a random value pointing to the
// object we're waiting to become freed.
return(false);
}
// Send a message to the collected object.
Messaging.void_objc_msgSend(notifierHandle, Selector.GetHandle("notify"));
Assert.IsTrue(isNotified, "notified");
// We're done. Cleanup.
NSRunLoop.Main.RunUntil(NSDate.Now.AddSeconds(0.1));
// Don't verify cleanup, it's not consistent.
// And in any case it's not what this test is about.
// Assert.IsTrue (isDeallocated, "released");
return(true);
}
