Understanding side effects

In the Using Scaffold() to structure your screen section of Chapter 6, Putting Pieces Together, I showed you how to display a snack bar using rememberCoroutineScope {} and scaffoldState.snackbarHostState.showSnackbar(). As showSnackbar() is a suspending function, it must be called from a coroutine or another suspending function. Therefore, we created and remembered CoroutineScope using rememberCoroutineScope() and invoked its launch {} function.

Invoking suspending functions

The LaunchedEffect() composable is an alternative approach for spawning a suspending function. To see how it works, let's look at the LaunchedEffectDemo() composable. It belongs to the EffectDemo sample, as illustrated in the following screenshot:

Figure 7.1 – The EffectDemo sample showing LaunchedEffectDemo()

LaunchedEffectDemo() implements a counter. Once the Start button has been clicked, a counter is incremented every second. Clicking on...