So I did a stepper in Compose and followed an exam...

# compose

[codeslubber]

So I did a stepper in Compose and followed an example where I had the state in the Composable method, then called a stepper function and passed it the state. Worked in 03, does not compile in 04, tells me I cannot mutate a val.

@Composable
fun MeasureQuestionView() {
    val typography = (MaterialTheme.typography())

    val rangeOfValues = 115..125
    val currentValue = state {rangeOfValues.first}

    Card(shape = RoundedCornerShape(8.dp)) {
        Column(modifier = Spacing(16.dp)) {
            Text("What was your blood sugar reading?", style = typography.h6)
            numberStepper(currentValue, rangeOfValues, "mg/dL")
        }
    }

}

@Composable
fun numberStepper(currentValue: State<Int>, range: IntRange, units: String) {
    val typography = (MaterialTheme.typography())

    Container(height = 75.dp) {
        Row(Spacing(20.dp)) {
            Button(text = "-", onClick = {
                if (currentValue.value > range.first) {
                    currentValue.value -= 1
                }
            })
            Spacer(LayoutWidth(10.dp))
            Text(currentValue.value.toString(), style = typography.h5)
            Spacer(LayoutWidth(10.dp))
            Button(text = "+", onClick = {
                if (currentValue.value < range.last) currentValue.value += 1
            })
            Spacer(LayoutWidth(10.dp))
            Align(Alignment.CenterLeft){
                Text(units)
            }
        }
    }

}

[Adam Powell]

The old State<T> has been split into State<T> and MutableState<T> to match the usual kotlin collection interfaces

[Adam Powell]

looks like you now want MutableState<T> in your stepper function parameter list

[Adam Powell]

(since State<T>.value is indeed now a val)

[codeslubber]

strange that ever worked? ok thanks @Adam Powell! compiles now…

[Adam Powell]

there was only one interface with var in -dev03 🙂

[Adam Powell]

the state {} factory returns MutableState so if you were relying on inference and refactored, that would do it