Text is always “my age is 0” (never changed). why?...

# compose

[Taeho Kim]

Text is always “my age is 0” (never changed). why? it’s bug?

class MainActivity : ComponentActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContent {
        var age by remember { mutableStateOf(0) }
        val person by remember {
          derivedStateOf { "my age is $age" }
        }
        Column(modifier = Modifier.padding(16.dp))  {
          Button(onClick = {
            age += 1
            Log.e("person", person)
          }) {

            Text(text =   person)
          }
          Text(
            text = person)
        }
    }
  }
}

[Hugo Bernardi]

Content of remember is only execute once without a specific key

val person by remember(key = age) {
   derivedStateOf { "my age is $age" }
}

+ maybe you don't have to use a derivedState for this case

[Zun]

Yeah you don’t need derivedState for this

[Gordon]

It looks like a bug, cos it works for me (compose-ui: 1.2.0), no change made to code.

[Gordon]

And it should work, since from my understanding:

var stateVariable by remember {
        derivedStateOf {
            // any state read within this block will cause this block
            // to be re-executed.
        }
    }

[Gordon]

But you right, that in this case, you don't really need derrivedStateOf.

[Taeho Kim]

Thanks. guys. (Especially Gordon)
It works in 1.2.0, but doesnt work 1.3.0.
And….It works in 1.3.1. ^^
maybe it was a bug.

[agrosner]

Anything in a remember must be passed down explicitly from my experience otherwise it’ll just remember it once. Since you wrap the derived state

[agrosner]

It’s not receiving new value from the remember memo