ViewModel 值更改处理程序代码重复

Question

我有以下 ViewModel：

data class Input(
  val email: String = "",
  val password: String = ""
)

class LoginViewModel : ViewModel() {
  private val _input = MutableStateFlow(Input())
  val input = _input.asStateFlow()

  fun onEmailChange(value: String) {
      _input.value = _input.value.copy(email = value)
  }

  fun onPasswordChange(value: String) {
      _input.value = _input.value.copy(password = value)
  }
}

我不喜欢onEmailChange 和onPasswordChange 的方法，因为我必须为Input 类的每个属性复制这样的代码。我想知道我是否可以让它更短并且没有代码重复？

我的可组合：

@Composable
fun LoginScreen(loginViewModel: LoginViewModel = viewModel()) {
    val input by loginViewModel.input.collectAsState()
    Column {
        TextField(
            label = { Text("Email") },
            value = input.email,
            onValueChange = loginViewModel::onEmailChange,
            singleLine = true
        )
        TextField(
            label = { Text("Password") },
            value = input.password,
            onValueChange = loginViewModel::onPasswordChange,
            singleLine = true
        )
    }
}

Answer 1

你可以改成这样：

fun onInputChange(
    email: String? = null,
    password: String? = null
) {
    val oldInput = _input.value
    _input.value = oldInput.copy(
        email = email ?: oldInput.email,
        password = password ?: oldInput.password,
    )
}