I have a problem with what I thought would be a si...

# compose

[Colton Idle]

I have a problem with what I thought would be a simple example I tried to write up for compose.

If you are well versed in mutableStateListOf I could use your help. Code in thread.

[Colton Idle]

My composable is basically a helper/wrapper composable that is a password input field but also contains a list of "Validations" below it to show to the user

data class Validations(val text: String, val validated: Boolean)

@Composable
fun PasswordVerifierInputField(
    value: String,
    change: (String) -> Unit,
    validations: List<Validations>
) {
    TextField(value = value, onValueChange = { change(it) })
    validations.forEach { Text(it.text, color = if (it.validated) Color.Green else Color.Red) }
}

This is the invoking code

var myText by remember { mutableStateOf("") }

val myValidations =
    mutableStateListOf(
        Validations("8 chars", false), Validations("Special char", false))

PasswordVerifierInputField(
    myText,
    { update ->
        myText = update
        if (myText.isNotBlank()) {
            // switch first validation to true as an example
            myValidations[0] = myValidations[0].copy(validated = true)
        }
    },
    myValidations)

For some reason, the 0th place validation text doesn't change colors

Also, does anyone have tips on whether I should keep Validations as a data class, or should that end up being a class that internally has 2 mutableStateOfs in it (one for text, and one for boolean)

[Nathan Castlehow]

Could it be due to not remembering the mutableStateListOf?

[Abhishek Dewan]

my first guess would be what nathan said. it seems like recomposing would cause you to reset your validations. as for the second question i would do it the way you have it currently. modeling your validation as a data model is the way to go imo

[Colton Idle]

I tried remembering and now I get

Type 'SnapshotStateList<Validations>' has no method 'setValue(Nothing?, KProperty<*>, [ERROR : Type from delegate])' and thus it cannot serve as a delegate for var (read-write property)

[Nathan Castlehow]

does it look something like below?

val myValidations = remember { mutableStateListOf(
        Validations("8 chars", false), Validations("Special char", false)) }

[Colton Idle]

Yep. Exactly that.

[Colton Idle]

I actually just tried to make a list of strings just to see if the compile error had to do with Validations class, but even a list of strings isn't working?

var myValidations by remember { mutableStateListOf("") }

Type 'SnapshotStateList<String>' has no method 'setValue(Nothing?, KProperty<*>, [ERROR : Type from delegate])' and thus it cannot serve as a delegate for var (read-write property)

[Colton Idle]

My imports include the following

import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateListOf
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue

[Nathan Castlehow]

change above to val and = instead of by

[Nathan Castlehow]

and see if that works

[Colton Idle]

Yeah.

val myValidations = remember { mutableStateListOf("") }

works

[Colton Idle]

Oh sorry. I didn't notice your original code had that as well. My bad

Updated mine to

val myValidations = remember { mutableStateListOf(
        Validations("8 chars", false), Validations("Special char", false)) }

just now and it compiles!

Time to test!

[Colton Idle]

It works! Thanks! A few more questions if anyone is still around

1. If my mutableStateListOf validations is in my viewModel... I don't have to surround it with remember {}... right?
2. myValidations[0] = myValidations[0].copy(validated = true) seems kinda clunky. No better way than this I suppose?

[Nathan Castlehow]

Correct. Remember helps the values exist across recompositions. The view models are outside of this process.

[Nathan Castlehow]

In regards to 2. Perhaps there is scope to use a derived state of that reads the current value and then checks the validation rules

[Nathan Castlehow]

Re why the = worked before it has to do with kotlin delegates (which i need to read up on more)

[Colton Idle]

@Nathan Castlehow alright thanks again for all the help.

The question that started off this entire chain is actually that my team member is insisting that the composable actually takes care of the validations itself. It's a highly specific component and that state actually isn't needed anywhere else, so onValueChange we want to run the validators inline... but we get a ConcurrentModificationException. Any ideas why changing modifying in onValueChanged won't work?

[Colton Idle]

I just gave up on trying to do the above ^

Bigger fish to fry and I guess I should really pass that event up anyway. /shruggie