양식 상태 관리

한 필드에서 양식으로

여러 개의 독립적인 상태

@Composable
fun LoginForm() {
    var email by remember { mutableStateOf("") }
    var password by remember { mutableStateOf("") }

    Column {
        OutlinedTextField(email, { email = it }, label = { Text("Email") })
        OutlinedTextField(password, { password = it }, label = { Text("Password") })
    }
}

데이터 클래스로 상태 묶기

data class SignUpState(
    val name: String = "",
    val email: String = "",
    val agreedToTerms: Boolean = false
)

copy()로 업데이트하기

var form by remember { mutableStateOf(SignUpState()) }

OutlinedTextField(
    value = form.name,
    onValueChange = { form = form.copy(name = it) },
    label = { Text("Name") }
)

전체 데이터 클래스 폼

var form by remember { mutableStateOf(SignUpState()) }

Column {
    OutlinedTextField(
        value = form.name,
        onValueChange = { form = form.copy(name = it) },
        label = { Text("Name") }
    )
    OutlinedTextField(
        value = form.email,
        onValueChange = { form = form.copy(email = it) },
        label = { Text("Email") }
    )
}

체크박스와 스위치

var form by remember { mutableStateOf(SignUpState()) }

Row(verticalAlignment = Alignment.CenterVertically) {
    Checkbox(
        checked = form.agreedToTerms,
        onCheckedChange = { form = form.copy(agreedToTerms = it) }
    )
    Text("I agree to the terms")
}

상태에서 값 도출하기

var form by remember { mutableStateOf(SignUpState()) }

val canSubmit by remember {
    derivedStateOf {
        form.name.isNotBlank() &&
        form.email.isNotBlank() &&
        form.agreedToTerms
    }
}

Button(onClick = { /* submit */ }, enabled = canSubmit) {
    Text("Sign Up")
}

구성 변경에도 상태 유지하기

var email by rememberSaveable { mutableStateOf("") }

OutlinedTextField(
    value = email,
    onValueChange = { email = it },
    label = { Text("Email") }
)

폼 상태를 ViewModel로 끌어올리기

class SignUpViewModel : ViewModel() {
    var state by mutableStateOf(SignUpState())
        private set

    fun onNameChange(value: String) {
        state = state.copy(name = value)
    }
}

ViewModel 연결하기

@Composable
fun SignUpScreen(vm: SignUpViewModel = viewModel()) {
    OutlinedTextField(
        value = vm.state.name,
        onValueChange = vm::onNameChange,
        label = { Text("Name") }
    )
}

순수 Kotlin: copy() 동작 확인하기

data class SignUpState(
    val name: String = "",
    val email: String = ""
)

fun main() {
    var state = SignUpState()
    state = state.copy(name = "Ada")
    state = state.copy(email = "ada@dev.io")
    println(state)
}

빠른 확인

복습