Add asStateFlow to the StateFlow variables in ViewModel class

[kaungkhantsoe]

Why

Currently, we define the StateFlow variables inside the ViewModel as follows:

val uiModels: StateFlow<List<UiModel>> = _uiModels

One issue with this approach is we can still convert the StateFlow variable to a MutableStateFlow in the other classes

val mutableUiModels = viewModel.uiModels as MutableStateFlow

We can ' emit ' new values once we can cast them to MutableStateFlow which we should not allow.

val coroutineScope = rememberCoroutineScope()
LaunchedEffect(key1 = Unit) {
    coroutineScope.launch {
        mutableUiModels.emit(listOf())
    }
}

If we were implementing an SDK, this could be an issue. One way to restrict such conversion would be using asStateFlow extension. If we look into the definition of asStateFlow, we will see the following code 👇

/**
 * Represents this mutable state flow as a read-only state flow.
 */
public fun <T> MutableStateFlow<T>.asStateFlow(): StateFlow<T> =
    ReadonlyStateFlow(this, null)

That way we can restrict the conversion of StateFlow to MutableFlow by defining the variables in ViewModel like the following:

private val _uiModels = MutableStateFlow<List<UiModel>>(emptyList())
val uiModels = _uiModels.asStateFlow()

Who benefits?

Android developers

[AVI5HEK]

Currently, we define the StateFlow variables inside the ViewModel as follows:

val uiModels: StateFlow<List<UiModel>> = _uiModels.asStateFlow()

You mean, currently we define it like this, right?

val uiModels: StateFlow<List<UiModel>> = _uiModels

[kaungkhantsoe]

@AVI5HEK Correct. We can even shorten the declaration like this.

val uiModels = _uiModels.asStateFlow()

[luongvo]

val uiModels = _uiModels.asStateFlow()

This style looks good to me. Voted 👍

[chornerman]

Voted 🚀

[manh-t]

Agreed. The Kotlin doc also has an example code like this.

However, we should update the description to be correct as @AVI5HEK mentioned, @kaungkhantsoe .

We should remove asStateFlow here so the other devs aren't confused because the current code doesn't have it.

[luongvo]

Exactly, I think we should suggest to change from

val uiModels: StateFlow<List<UiModel>> = _uiModels

to

val uiModels = _uiModels.asStateFlow()

[kaungkhantsoe]

Updated 🚀 @manh-t @luongvo

[Wadeewee]

Agreed and Voted 🚀

[thiennguyen0196]

Agreed and voted ✋

[ryan-conway]

Issue created 🙏🏻