Hey, I try to understand, I use `instanceKeeper` f...

# mvikotlin

[lehakorshun]

Hey, I try to understand, I use instanceKeeper for reusing Store and in init I add lifecycle.doOnDestroy(citiesStore::dispose)
of cause, it doesn’t work after configuration was changed. when should I dispose my store, if I reuse instance via instanceKeeper?

[Arkadii Ivanov]

Hello! This case is covered in samples: https://github.com/arkivanov/MVIKotlin/blob/41a47c0fb022bc79312053d7605f83a02e1b5df7/sample/todo-reaktive/src/commonMain/kotlin/com/arkivanov/mvikotlin/sample/todo/reaktive/controller/TodoListReaktiveController.kt#L36

Also you can check samples in the docs: https://arkivanov.github.io/MVIKotlin/state_preservation.html

In general:
• To retain a Store you can use getOrCreateStore extension function: https://github.com/arkivanov/MVIKotlin/blob/41a47c0fb022bc79312053d7605f83a02e1b5df7/mvikotlin/src/commonMain/kotlin/com/arkivanov/mvikotlin/core/instancekeeper/InstanceKeeperExt.kt#L33
• To retain an arbitrary object you can use getOrCreate extension function: https://github.com/arkivanov/MVIKotlin/blob/41a47c0fb022bc79312053d7605f83a02e1b5df7/mvikotlin/src/commonMain/kotlin/com/arkivanov/mvikotlin/core/instancekeeper/InstanceKeeperExt.kt#L17 . It provides you a wrapped Lifecycle that is destroyed then when the object is completely gone.

[lehakorshun]

yes, I saw it, and in your sample you don’t dispose ListStore when lifecycle call onDestroy

[lehakorshun]

maybe it is overhead, but I want to dispose all my store when lifecycle call onCleared method on ViewModel.

[Arkadii Ivanov]

It should be destroyed when the related ViewModel is cleared. That's the whole purpose of the extension.

[Arkadii Ivanov]

Here is the related test: https://github.com/arkivanov/MVIKotlin/blob/41a47c0fb022bc79312053d7605f83a02e1b5df7/mvikotlin-extensions-androidx/src/androidTest/kotlin/com/arkivanov/mvikotlin/extensions/androidx/instancekeeper/AndroidInstanceKeeperTest.kt#L27

[Arkadii Ivanov]

So the Store supposed to be destroyed when the Lifecycle is destroyed and the Store is not retained anymore (its ViewModel is cleared). But when the Store is retained, it should not be disposed.

[lehakorshun]

ok go step by step 🙂
in the sample you call todoAddStore::dispose on every doOnDestroy call. but why you don’t call the dispose method for list store?

[Arkadii Ivanov]

Because the TodoListStore is retained, but the TodoAddStore is not.

[lehakorshun]

I think we don’t have to dispose AddSotre too

[Arkadii Ivanov]

The it will be leaked?

[Arkadii Ivanov]

In the next instance of the controller there will a new instance of the TodoAddStore

[lehakorshun]

yes. but what will leaked?

[lehakorshun]

it is similar to the list store

[Arkadii Ivanov]

So every Store should be destroyed at the end of its own lifecycle. TodoListStore has a lifecycle equal to a ViewModel. So it is disposed when the ViewModel is cleared, normally when the screen is closed. But TodoAddStore has a lifecycle equal to screen. So it should be disposed when the screen is destroyed, e.g. when configuration change.

[lehakorshun]

I fully agree. But I can’t find place where

So it is disposed when the ViewModel is cleared

is called

[Arkadii Ivanov]

When the list screen is rotated, then TodoListStore instance is retained - passed to the new instance of the list screen. So it is not disposed at this point. But TodoAddStore is not retained. When the new instance of the screen is created, a new instance of TodoAddStore is created as well. So previous instance of TodoAddStore is disposed.

[Arkadii Ivanov]

The getOrCreate extension method provides another Lifecycle , which is destroyed when the ViewModel is cleared: https://github.com/arkivanov/MVIKotlin/blob/41a47c0fb022bc79312053d7605f83a02e1b5df7/mvikotlin/src/commonMain/kotlin/com/arkivanov/mvikotlin/core/instancekeeper/InstanceKeeperExt.kt#L17

Each InstanceKeeper has a Lifecycle https://github.com/arkivanov/MVIKotlin/blob/41a47c0fb022bc79312053d7605f83a02e1b5df7/mvikotlin/src/commonMain/kotlin/com/arkivanov/mvikotlin/core/instancekeeper/InstanceKeeper.kt#L15

[lehakorshun]

thx. I need to check this point 🙂

[lehakorshun]

@Arkadii Ivanov thx for explanations,, i didn’t see dispose in this peace of code

getOrCreate { lifecycle ->
        val store = factory()
        lifecycle.doOnDestroy(store::dispose)
        store
    }

[Arkadii Ivanov]

You are welcome!