ErrorSafe Pattern

errorSafe bundles a field's current value, its original value, and its error message into one remember-able unit — eliminating three separate state variables per field.

The ErrorSafeValue<T> data class

Declaring state

var firstName by remember { errorSafe("") }
var email     by remember { errorSafe(existingUser?.email ?: "") }

The argument to errorSafe becomes both the initial value and the baseline for modified.

Reading and writing

// Read
Text(firstName.value)

// Write — copy to preserve other fields
firstName = firstName.copy(value = newValue)

// Clear error
firstName = firstName.copy(error = null)

Wiring to a text field

AppTextField(
    label = "First Name",
    value = firstName.value,
    onChange = { firstName = firstName.copy(value = it) },
    errorMessage = firstName.error
)

Checking dirty state

modified is true as soon as the user changes the value from its starting point:

val isDirty = firstName.modified || email.modified

Button(enabled = isDirty, onClick = { ... }) {
    Text("Save")
}

This is useful for preventing unnecessary API calls when nothing has changed, or for showing a discard-changes prompt.

Wiring errors from the validator

The onError callback on each ValidationField receives the error string (or null on success). Copy it onto the matching state:

ValidationField(
    value = email.value,
    name = "Email",
    type = FormValidator.Type.Email
) { errorMessage ->
    email = email.copy(error = errorMessage)
}