events.md

Uniflow 🦄- Simple Unidirectionnel Data Flow for Android & Kotlin

Applying side effects with Events

The same way we define States, we define events from UIEvent class, as immutable Kotlin data:

// Events definition
sealed class WeatherEvent : UIEvent() {
    data class Success(val location: String) : WeatherEvent()
    data class Failed(val location: String, val error: Throwable? = null) : WeatherEvent()
}

When you don't want to update the current state, you can simply send an event with sendEvent() function:

fun getWeather() = action {
    
    // send event
    sendEvent(WeatherEvent.Success(location))
}

To observe events from your Activity/Fragment view class, use the onEvent function with your ViewModel instance:

class MyActivity : AppCompatActivity(){

    fun onCreate(...) {
        
        // Let's observe incoming events
        onEvents(viewModel) { event ->
            when (event) {
                is WeatherListUIEvent.Success -> showSuccess(event.location)
                is WeatherListUIEvent.Failed -> showFailed(event.location, event.error)
            }
        }
    }
}

Warning: An event is "one shot". It won't persist in the current Dataflow. Once consumed, an event is cleared from the Dataflow

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