MakePaymentScreen.kt

/* Copyright 2022 Google LLC.	
   SPDX-License-Identifier: Apache-2.0 */

//////////////////////////////////////////////
// Jetpack Compose code
//////////////////////////////////////////////

@Composable
fun MakePaymentScreen(
    onPaymentMade: (PaymentModel, Boolean) -> Unit,
    viewModel: MakePaymentViewModel = viewModel()
) {
    val uiState by viewModel.uiState.collectAsState()

    uiState.paymentResult?.let {
        val currentOnPaymentMade by rememberUpdatedState(onPaymentMade)
        LaunchedEffect(uiState) {
            // Tell the caller composable that the payment was made.
            // the parent composable will act accordingly.
            currentOnPaymentMade(
                uiState.paymentResult.paymentModel, 
                uiState.paymentResult.isPaymentSuccessful
            )
        }
    }

    // Rest of the UI for the login screen.
}


//////////////////////////////////////////////
// Activity / Views code
//////////////////////////////////////////////

class MakePaymentActivity : AppCompatActivity() {
    private val viewModel: MakePaymentViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        /* ... */
        lifecycleScope.launch {
            repeatOnLifecycle(Lifecycle.State.STARTED) {
                viewModel.uiState.collect { uiState ->
                    if (uiState.paymentResult != null) {
                        val intent = Intent(this, PaymentResultActivity::class.java)
                        intent.putExtra(
                            "PAYMENT_RESULT", 
                            uiState.paymentResult.isPaymentSuccessful
                        )
                        startActivity(intent)
                        finish()
                    }
                }
            }
        }
    }
}

Is rememberUpdatedState on line 16 of rev 3 necessary? My understanding is that this construct is only necessary if the reference is captured for use at a later time like in a long-running coroutine within the effect. Here the launched effect is evaluated immediately.

[Actually I see it is carried over from rev 2 where it did have a purpose when referenced in a lifecycle observer. Perhaps it is no longer needed.]