Hello, World! Isn't there a version of `String.map` fun that returns a String (instead of the generi...

# announcements

[bod]

Hello, World! Isn't there a version of String.map fun that returns a String (instead of the generic one returning a List<R>) somewhere?

[bod]

I guess I can use .toCharArray().concatToString()... 🙂

[agrosner]

somestring.let { s -> someOtherstring }? return whatever you want from let, it could also be the same data

[Shawn]

I think you could make something work with fold actually

[Nir]

you can just do .map.joinToString can't you

[Nir]

actually joinToSTring already takes a transforming function

[Nir]

"hello".toList().joinToString { it.toUpperCase() }

[Nir]

I'm actually not sure why the toList is necessary

[Shawn]

because joinToString() is defined on Iterable rather than String or CharSequence

[Nir]

Yeah, just realized, the map on CharSequence is a separate thing

[Nir]

this obviously begs the question why CharSequence is its own thing or at least why does CharSequence not at least inherit from Iterable<Char>

[Nir]

Or Sequence<Char>

[Nir]

My past experience is that every time I see something like this that makes no sense the answer is "because Java" so I'll assume that this is the reason here

[Nir]

ding ding ding: https://discuss.kotlinlang.org/t/why-doesnt-charsequence-implement-iterable/2485

[bod]

sorry I wasn't very clear!

My need was to map chars inside a String to other chars (my specific case: making a String suitable for a file name, so each illegal character is replaced with a space.)

[bod]

I ended up doing this:

fun String.asValidFatFileName(): String = map { if (it.isValidFatFileNameChar()) it else ' ' }.toCharArray().concatToString()

but originally I was a bit surprised that

fun String.asValidFatFileName(): String = map { if (it.isValidFatFileNameChar()) it else ' ' }

wasn't enough

[Nir]

yeah, the string API is IMHO hugely confusing

[Nir]

.filter returns a string but .map returns a List<Char> 😞

[Nir]

anyway just add joinToString(separator="")