Kotlin, how can I make my code shorter in this spaghetti code? - kotlin

Question

I'm working on readlines now and can I make this few if's shorter? I'm making a validation to what user is sending to me. The filed cant be empty or null. I have 3 important things that user has to write in field and every three times I have to check the same... .
fun readlinesToAddEntryAndValidation(): List<String> {
println(ENTER_DESCRIPTION_ID_TEKST)
val entryId: String? = readLine()
if (!entryId.isNullOrEmpty()) {
println(ENTER_DESCRIPTION_NAME_TEKST)
val name: String? = readLine()
if (!name.isNullOrEmpty()) {
println(ENTER_DESCRIPTION_TEKST_TEKST)
val tekst: String? = readLine()
if (!tekst.isNullOrEmpty()) {
return listOf(entryId, name, tekst)
} else {
println(EMPTY_READLINE_ERROR)
return readlinesToAddEntryAndValidation()
}
} else {
println(EMPTY_READLINE_ERROR)
return readlinesToAddEntryAndValidation()
}
} else {
println(EMPTY_READLINE_ERROR)
return readlinesToAddEntryAndValidation()
}
}

Answer 1

Try to avoid cognitive complexity one of the things is avoid nesting. Also when an if always returns something. An else statement is not needed
fun readlinesToAddEntryAndValidation(): List<String> {
println(ENTER_DESCRIPTION_ID_TEKST)
val entryId: String? = readLine()
if (entryId.isNullOrEmpty()) {
println(EMPTY_READLINE_ERROR)
return readlinesToAddEntryAndValidation()
}
println(ENTER_DESCRIPTION_NAME_TEKST)
val name: String? = readLine()
if (!name.isNullOrEmpty()) {
println(ENTER_DESCRIPTION_TEKST_TEKST)
val tekst: String? = readLine()
if (!tekst.isNullOrEmpty()) {
return listOf(entryId, name, tekst)
}
}
println(EMPTY_READLINE_ERROR)
return readlinesToAddEntryAndValidation()
}

Answer 2

You could do something like this:
fun readlinesToAddEntryAndValidation() : List<String> {
fun read(message: String): String? {
println(message)
val line = readLine()
return if (line.isNullOrEmpty()) null else line
}
read(ENTER_DESCRIPTION_ID_TEKST)?.let { entryId ->
read(ENTER_DESCRIPTION_NAME_TEKST)?.let { name ->
read(ENTER_DESCRIPTION_TEKST_TEKST)?.let { tekst ->
return listOf(entryId, name, tekst)
}
}
}
println(EMPTY_READLINE_ERROR)
return readlinesToAddEntryAndValidation()
}
I wouldn't normally recommend nesting too much, but I feel like that's fairly readable with only three parameters, and the null checking means it short-circuits as soon as you run into a problem.

Answer 3

Making user to reenter all previous (independent!) values after his mistake in the middle of the input is a bad UI.
If user failed to correctly input some entry, you need to ask him to reenter only this single item (until he eventually do it right):
fun read(inputMessage: String, errorMessage: String = EMPTY_READLINE_ERROR): String {
println(inputMessage)
var line: String? = readLine()
while (line.isNullOrEmpty()) {
println(errorMessage)
println(inputMessage)
line = readLine()
}
return line
}
With this auxilary function, whole program become a single-liner:
fun readlinesToAddEntryAndValidation() =
listOf(
ENTER_DESCRIPTION_ID_TEKST,
ENTER_DESCRIPTION_NAME_TEKST,
ENTER_DESCRIPTION_TEKST_TEKST
).map { read(it) }