Why needn't the author to wrap text.isNotBlank() with remember?-CodePudding

The Code A is from the official Sample project here.

1: I think I can wrap text.isNotBlank() withremember, so I think Code B is good, right?

BTW, I know the system will re-calculate when the text ( val (text, setText) = remember { mutableStateOf("") } ) is changed. So

2: In Code B, val (icon, setIcon) = remember { mutableStateOf(TodoIcon.Default)} and val iconsVisible = remember {text.isNotBlank() } will be re-launched when the text is changed (val (text, setText) = remember { mutableStateOf("") }) , right?

Code A

@Composable
fun TodoItemInput(onItemComplete: (TodoItem) -> Unit) {
   val (text, setText) = remember { mutableStateOf("") }
   val (icon, setIcon) = remember { mutableStateOf(TodoIcon.Default)}
   val iconsVisible = text.isNotBlank()
   Column {
       Row( /* ... */ ) {
           /* ... */
       }
       if (iconsVisible) {
           AnimatedIconRow(icon, setIcon, Modifier.padding(top = 8.dp))
       } else {
           Spacer(modifier = Modifier.height(16.dp))
       }
   }
}

Code B

@Composable
fun TodoItemInput(onItemComplete: (TodoItem) -> Unit) {
   val (text, setText) = remember { mutableStateOf("") }
   val (icon, setIcon) = remember { mutableStateOf(TodoIcon.Default)}
   val iconsVisible = remember {text.isNotBlank() } //I add  remember 
   Column {
       ...
   }
}

CodePudding user response：

If you use remember as in Code B, iconsVisible will be calculated only once and the same value will be used across all recompositions and not get updates when text changes, which is not what we want here.

If you want to use remember here, you should pass text as a key to it, remember(text) { text.isNotBlank() }. But as this is not a time consuming calculation, you can just skip the remember block and use it as in Code A. The .isNotBlank() function will be invoked in every recomposition but that doesn't matter much here.