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kotlinlang

Hi guys. I’m playing with Snapshot System.
I tried to modify a mutable state in global snapshot, but the apply listener doesn’t get called back. Code in:thread:

Here is my code:
```val globalWriteObserverHandler = Snapshot.registerGlobalWriteObserver {
  println("on global written")
  Snapshot.sendApplyNotifications()
}
val applyObserverHandler = Snapshot.registerApplyObserver { set, _ -&gt;
  println("on applied - $set")
}
val count = mutableStateOf(0)
count.value = 1
globalWriteObserverHandler.dispose()
applyObserverHandler.dispose()```


If I take a snapshot before the modification and dispose the snapshot immediately, then the apply listener can get called back when state is modified:
```...
val count = mutableStateOf(0)
// added this line
Snapshot.takeSnapshot().dispose()
count.value = 1
...```
Dose anyone know the reason?

I found it’s due to the logic in `fun &lt;T : StateRecord&gt; T.overwritableRecord`.
```internal fun &lt;T : StateRecord&gt; T.overwritableRecord(
    state: StateObject,
    snapshot: Snapshot,
    candidate: T
): T {
    ...

    if (candidate.snapshotId == id) return candidate

    ...

    snapshot.recordModified(state)

    return newData
}```
When candidate record is found, it returns, without calling `recordModified`. Is this expected? If yes, what the reason?

I’m guessing yea, because the snapshot system is designed only to let observers know _if_ an object has been modified, not _how many times_ it’s been modified, in a given snapshot. If an object is modified many times in a snapshot, there are probably major performance wins to this approach.

I see. It makes sense. But I still feel that the behavior is a little bit buggy in my first code snippet. I expect there would be at least one apply notification.

Look at the kdoc for initializeObjects and sendApplyNotifications in Snapshot.kt. Changes aren't recorded for brand new state objects until the snapshot is applied or initializeObjects is called. 

`initializeObjects`? I’m guessing you mean `notifyObjectsInitialized`. And it works. Thanks very much!