rem

Facilitates in-memory object retention with ViewModel, avoiding Parcelable. Supports ViewModel state restoration upon screen rotation and offers scoped ViewModel management and cleanup.

#viewmodel
#compose-multiplatform

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Android JVMJVMWasm

GitHub stars0

Authorsshirozatou

Open issues0

Creation dateabout 1 year ago

Last activity3 months ago

Latest release1.2.0 (3 months ago)

GitHub repository

rem

Remember any type of object with ViewModel. No Parcelable, just in-memory. (Why not?)

Dependency

implementation("io.github.shirozatou:rem:1.2.0")

Usage

remember {
    Any() // ❌ Evaluated again when screen rotated
}
rememberSaveable {
    Any() // ❌ IllegalArgumentException. Cannot be stored to Bundle (Android)
}
rememberWithViewModel {
    Any() // 🥳 Restore from ViewModel when screen rotated
}

Remembered value is forget when

once goes out of scope
key changed
viewModel in current scope is cleared

Clean up

Currently only instance of Clearable is allowed.

var flag by remember { mutableStateOf(true) }
if (flag) {
    val foo = rememberWithViewModel(key) {
        object : Clearable {
            val data = Any()
            override fun onCleared() {
                // Called on main thread once flag == false
            }
        }
    }.data
}

Can I remember ViewModel with rememberWithViewModel?

ViewModel should be managed by ViewModelStoreOwner

For scoped ViewModel, use ScopedViewModelStore:

ScopedViewModelStore {
    val v1 = viewModel<YourViewModel>()
    val v2 = viewModel<YourViewModel>()

    ScopedViewModelStore {
        val v3 = viewModel<YourViewModel>()

        assert(v1 === v2)
        assert(v1 !== v3)
    }
}

ScopedViewModelStore is a simple trick btw.

@Composable
fun ScopedViewModelStore(content: @Composable () -> Unit) {
    val viewModelStoreOwner = rememberWithViewModel {
        object : ViewModelStoreOwner, Clearable {
            override val viewModelStore: ViewModelStore = ViewModelStore()
            override fun onCleared() {
                viewModelStore.clear()
            }
        }
    }
    CompositionLocalProvider(
        LocalViewModelStoreOwner provides viewModelStoreOwner,
        content = content
    )
}

Solution for LazyList

ScopedSaveableStateRegistry {
    LazyColumn {
        items(count = 100) {
            val remembered = rememberSaveable {
                Any() // You can remember any type of object here
            }
            val notRemembered = rememberWithViewModel {
                Any()
            }
            Text(text = remembered.toString())
            Text(text = notRemembered.toString())
        }
    }
}

Reminder

Similar to ViewModel, don't leak Context or something.