the error is "Error:(20, 35) Kotlin: Type mismatch: inferred type is (Int) -> Int but ((Int) -&gt...

# getting-started

[febs]

the error is "Error:(20, 35) Kotlin: Type mismatch: inferred type is (Int) -> Int but ((Int) -> CharSequence)? was expected".

Should I explicitly convert that to a CharSequence? Why? 🤔

[zpearce]

the definition of joinToString takes a lambda of type (T) -> CharSequence, so yeah, you have to return a String (CharSequence).

myArray.joinToString { (it*2).toString() }

[Tristan Caron]

Kotlin doesn't have implicit casts

[febs]

so bad, that's pretty ugly.

[febs]

println (mySecondArray.joinToString { (it*2).toString() } )

[febs]

this works. But stating "joinToString" and then casting toString again doesn't look very kotlinish. Hope they'll fix that 😄

[hudsonb]

It'd be pretty easy to create your own joinToString extension that works the way you describe

[hudsonb]

Assuming your data type is Array<Int>, you could create something like this:

fun Array<Int>.joinToString(separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: ((Int) -> Int)): String {
    return joinTo(StringBuilder(), separator, prefix, postfix, limit, truncated) { n -> transform.invoke(n).toString() }.toString()
}

Which would allow you to do println (myArray.joinToString { it*2 } ) like you want

[aarjav]

^ at that point I'd argue it's better to do Any than Int specifically

[hudsonb]

Sure