livedata-observe-usage-compose.kt

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            val hello = remember { HelloModel(HelloResult.Pending) }

            observe(getHello()) {
                onResult {
                    if(hello.state != result) hello.state = result
                }
            }

            hello.state.let { state ->
                when (state) {
                    is HelloResult.Pending -> Text("Loading...")
                    is HelloResult.Hello -> Text("Hello")
                    is HelloResult.Error -> Text("Error")
            }

        }
    }

    fun getHello(): LiveData<HelloResult> {
        return MutableLiveData(HelloResult.Hello())
    }

    sealed class HelloResult {
        object Pending : HelloResult()
        object Hello : HelloResult()
        object Error : HelloResult()
    }

    @Model
    data class HelloModel(
        var state: HelloResult = HelloResult.Pending
    )
}