I must miss something obvious, but why ``` var inputState: TextFieldValue by mutableStateOf(TextFi...

# compose

[dimsuz]

I must miss something obvious, but why

var inputState: TextFieldValue by mutableStateOf(TextFieldValue())

fails with an error

Type 'MutableState<TypeVariable(T)>' has no method 'getValue(Nothing?, KProperty<*>)' and thus it cannot serve as a delegate

[flosch]

Either var inputState: TextFieldValue = mutableStateOf(TextFieldValue()) or var inputState: TextFieldValue by remember { mutableStateOf(TextFieldValue()) }

[dimsuz]

both give the similar error 😞

[Daniel Sandström]

You need to import

androidx.compose.runtime.getValue
androidx.compose.runtime.setValue

[dimsuz]

great this worked, thanks!

What is the difference between using delegate and "remember"?

[flosch]

best to check out this code-lab: https://codelabs.developers.google.com/codelabs/jetpack-compose-basics/#4

[flosch]

delegation and remember cannot be compared.
remember can be called by delegation (`getValue`/`setValue`), mutableStateOf cannot.
Sorry scratch that, mutableStateOf , can be called by delegation

[dimsuz]

hmm. I can see this in the codelab:

var todoItems: List<TodoItem> by mutableStateOf(listOf())

no remember and delegation. But it doesn't work when I try to feed TextFieldValue like this

[dimsuz]

Only using by remember { mutableStateOf(...) } works

[flosch]

You should read through the code-lab to find out what remember { X } , mutableStateOf(X) and remember { mutableStateOf(X) } are doing.

[dimsuz]

They cause recomposition If value changes I guess. But I'm not sure I understand what's the point of by mutableStateOf then

[dimsuz]

will read this codelab in full then 🙂

[flosch]

You can read about delegated properties here. This is a kotlin thing, not a compose thing.

[dimsuz]

If by mutableStateOf simply adjusts property to delegate to state's get/set, then I don't understand why codelab's examples work without remember:

var todoItems: List<TodoItem> by mutableStateOf(listOf())

propagates changes to composables.

While if I do this with TextFieldValue it isn't propagating. only if I additionaly wrap in remember — then it does.