factory-function-the-problem.kt

// domain:
class PhoneNumber(val value: String)
class Contact(val phoneNumber: PhoneNumber)

// screen:
class PhoneNumberScreen(
    private val phoneNumber: PhoneNumber
) {

    fun render() {
        println("Phone number: ${phoneNumber.value}")
    }
}

// presentation layer:
fun main() {
    val contact = Contact(PhoneNumber("12345"))
    show(contact.phoneNumber) // "Phone number: 12345"

    val contactWithInvalidPhoneNumber = Contact(PhoneNumber(""))
    show(contactWithInvalidPhoneNumber.phoneNumber) // "Phone number: "
}

private fun show(phoneNumber: PhoneNumber) {
    val phoneNumberScreen = PhoneNumberScreen(phoneNumber)
    phoneNumberScreen.render()
}