UiState.copy lambda not returning UiState object

Question

I'm trying to set up a ViewModel but I'm having trouble updating UiState fields. The UiState.copy() function should return a modified UiState object but just returns unit.

I expect the value to change once the code runs. I cant get it to compile tough because the lambda body has the wrong return type.

This is my code:

class CalendarViewModel: ViewModel() {
    private val _calendarUiState = MutableStateFlow(CalendarUiState())
    val calendarUiState: StateFlow<CalendarUiState> = _calendarUiState.asStateFlow()

    fun test() {
        _calendarUiState.update(
            { calendarUiState -> calendarUiState.copy(currentDate = "new_date") }
        )
    }
}

I get this while hovering over the lambda:

Type mismatch.
Required:
CalendarUiState
Found:
Unit

Answer 1

The problem was in the UiState-Class, I didnt declare it as a data class. Check your UiState file if you have a similar problem