ViewModel

MediatorK works naturally with Android ViewModel — inject the mediator and dispatch requests from viewModelScope.

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Basic usage

class UserViewModel(private val mediator: Mediator) : ViewModel() {

    val user = MutableStateFlow<User?>(null)

    fun load(id: String) {
        viewModelScope.launch {
            user.value = mediator.send(GetUserQuery(id))
        }
    }
}

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With Koin

Declare the ViewModel in your Koin module and inject the mediator via get():

// koin module
viewModel { UserViewModel(get()) }

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Handling validation errors

When ValidationBehavior is in the pipeline, catch ValidationException and surface its message in your UI state:

class CreateTodoViewModel(private val mediator: Mediator) : ViewModel() {

    val error = MutableStateFlow<String?>(null)

    fun submit(title: String, dueDate: LocalDate) {
        viewModelScope.launch {
            try {
                mediator.send(CreateTodoCommand(title, dueDate))
            } catch (e: ValidationException) {
                error.value = e.message
            }
        }
    }
}

See Validation for how ValidationBehavior and ValidationException are set up.

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Next

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