What is the best way to convert pascal case string...

# announcements

[igor.wojda]

What is the best way to convert pascal case string into snake case string in Kotlin?
"apiBaseUrl" -> "api_base_url"

[pardom]

Split, map with capitalize, join?

[igor.wojda]

My issue is with splitting 🤔

[Robert Jaros]

https://github.com/pearxteam/kasechange

[pardom]

Oh, the inverse.

[karelpeeters]

str.split("(?=[A-Z])".toRegex()).joinToString("_") { it.toLowerCase() }

[pardom]

fun String.pascalToSnakeCase() = map { char ->
        if (char.isUpperCase()) "_${char.toLowerCase()}" else char
    }.joinToString("")

[Shawn]

"camelCase".split(Regex("(?=[A-Z])")).joinToString(separator = "_", transform = String::toLowerCase)

[Jonathan Mew]

I guess this might be considered less idiomatic:

val capitalRegex = "([A-Z])".toRegex()

    fun String.snakify() = this.replace(capitalRegex) {
        '_' + it.value.toLowerCase()
    }.trim('_')

    @Test
    fun `test pascalToSnake`() {
        "".snakify() shouldBe ""
        "abc".snakify() shouldBe "abc"
        "aBc".snakify() shouldBe "a_bc"
        "someThingElse".snakify() shouldBe "some_thing_else"
    }

[karelpeeters]

Looks like

str.split(Regex("(?=[A-Z])")).joinToString("_", String::toLowerCase)

compiles with the new type inference but not the old one, that's great!

[igor.wojda]

thanks @karelpeeters. This is exactly what I was missing. I am using old type interface (I guess) with kotling-gardle-dsl, but after small modification I made it work

str.split(Regex("(?=[A-Z])")).joinToString("_") { it.toLowerCase() }

[igor.wojda]

BTW @karelpeeters can you drop some link related to Kotlin old/new type inference ? What is the state - is it currently released, experimental?

[karelpeeters]

Here's the announcement that they turned it on in the IDE but not the actual compilation: https://blog.jetbrains.com/kotlin/2019/06/kotlin-1-3-40-released/