Trying to follow the guidance of treating events/effects as state <https://developer.android.com/jet...

# android

[Tash]

Trying to follow the guidance of treating events/effects as state https://developer.android.com/jetpack/guide/ui-layer/events#views_1

For some things where you need to be truly imperative with views, such as webView.goBackward()/webView.goForward(), how do you encode them as state? They’re very event-like and need to happen just once given certain conditions, and could get complicated when state objects are `data class`es and you use .copy to update parts of state. More in 🧵

[Tash]

For example, if you had:

data class State(val goBackInWebView: Boolean, val buttonColor: Color)

You might do something like:

// business logic change
state.copy(goBackInWebView = true) // setting it to true

// theme change
state.copy(buttonColor = Red) // goBackInWebView is still true

The first line causes goBackInWebView to be true, but after the second line, you might read the state where goBackInWebView is still true. Setting goBackInWebView = false in the second line where you’re changing a part of the state in response to a theme change only is weird.

OR: are `data class`es a bad option in this case, and a sealed class is better? Not sure what that would look like but something like

sealed class State {
    data class ColorChanged(val buttonColor: Color): State()
    object WebViewBack: State()
}

[Ben Trengrove [G]]

You can see an example of exactly that in Accompanist WebView, https://github.com/google/accompanist/blob/main/web/src/main/java/com/google/accompanist/web/WebView.kt

[Tash]

That’s super helpful; thank you!