Which one is standard for toggling `isLoading` val...

# android

[Rafiul Islam]

Which one is standard for toggling isLoading value before and after a network call and has no issues.

Option 1:

viewModelScope.launch {
    _uiState.update { it.copy(isLoading = true) }
    val result = getSomethingUseCase()
    if (result.isSuccess) {
        _uiState.update {
            it.copy(isLoading = false, data = result.getOrDefault(emptyList()))
        }
    } else {
        _uiState.update {
            it.copy(isLoading = false, errorMessage = Error.unknownError())
        }
    }
}

Problem: have to isLoading = false everything let's say I handle multiple types of error then with when block.

See more in the thread 🧵

[Rafiul Islam]

Option 2:

viewModelScope.launch {
    _uiState.update { it.copy(isLoading = true) }
    val result = getSomethingUseCase()
    _uiState.update { it.copy(isLoading = false) }
    if (result.isSuccess) {
        _uiState.update {
            it.copy(data = result.getOrDefault(emptyList()))
        }
    } else {
        _uiState.update {
            it.copy(errorMessage = Error.unknownError())
        }
    }
}

isLoading = false just after the network call even before updating the state

[Rafiul Islam]

Option 3:

viewModelScope.launch {
    try {
        _uiState.update { it.copy(isLoading = true) }
        val result = getSomethingUseCase()
        if (result.isSuccess) {
            _uiState.update {
                it.copy(data = result.getOrDefault(emptyList()))
            }
        } else {
            _uiState.update { it.copy(errorMessage = Error.unknownError()) }
        }
    } finally {
        _uiState.update { it.copy(isLoading = false) }
}

Using try and finally
Problem: Introducing an unnecessary try and finally block

[florent]

I use a sealed interface

[Rafiul Islam]

Do you think for a large project a sealed class/interface is more flexible, less error-prone, and easier to maintain than a property-based state?

[Himanshu Pal]

Yes.
What I do is define it like this

sealed class OResponseWrapper<out T> {
    data class Success<out T>(val data: T) : OResponseWrapper<T>()

    data class Error(val message: String? = null, val cause: Throwable? = null) :
        OResponseWrapper<Nothing>()

    data object Loading : OResponseWrapper<Nothing>()
}

And, in this case I'll do separate handlings for Success and Error state and instead of handling Loading state, I'll show loader in else block of when statement.

By doing this, suppose i added one more class later on as:

sealed class OResponseWrapper<out T> {
    data class Success<out T>(val data: T) : OResponseWrapper<T>()

    data class Error(val message: String? = null, val cause: Throwable? = null) :
        OResponseWrapper<Nothing>()

    data object Loading : OResponseWrapper<Nothing>()

    data object LoadingMore : OResponseWrapper<Nothing>()
}

This LoadingMore is used for showing progress when I am doing pagination in a recycler view. So, I'll handle this LoadingMore explicitly on the intended places only.