[Kotlin Flow] Using "launchIn" instead of "collect" for collecting Flows in ViewModel

[luongvo]

Why

Using launchIn instead of collect for collecting Flows in ViewModel is recommended way, because:

• collect() will block the coroutine until the flow has finished emitting. This behavior is sometimes desired, but it’s not in most cases.
• launchIn is less code to write, we don’t have to have indentations, and easier to understand.
• We can eliminate the execute operator in the BaseVIewModel.

Sample implementation:

        logInUseCase(
            email = email,
            password = password
        )
            .onStart { showLoading() }
            .onCompletion { hideLoading() }
            .catch { e -> _error.emit(e) }
            .onEach {
                _isLoggedIn.emit(true)
                navigateToHome()
            }
            .launchIn(viewModelScope)

RFC discussion: #408

References:

• https://handstandsam.com/2021/02/19/the-best-way-to-collect-a-flow-in-kotlin-launchin/
• https://itnext.io/differences-in-methods-of-collecting-kotlin-flows-3d1d4efd1c2

Who Benefits?

Developers