How do I convert Array <T?>? in Array <T> in Kotlin
I am taking my first steps in Kotlin and trying to write a simple string splitting function. I started with this:
fun splitCSV(s : String) : Array<String> {
return s.split(",");
}
Which I think could also be written like this:
fun splitCSV(s : String) : Array<String> = s.split(",");
But I am getting a type error since s.split is returning Array<String?>?
, not Array<String>
. I couldn't find an easy way to do the cast, so I wrote this function to convert:
fun forceNotNull<T>(a : Array<T?>?) : Array<T> {
return Array<T>(a!!.size, { i -> a!![i]!! });
}
fun splitCSV(s : String) : Array<String> = forceNotNull(s.split(","));
However, I am now getting a runtime error:
ClassCastException: [Ljava.lang.Object; cannot be applied to [Ljava.lang.String
If I change T in forceNotNull
to String then it works, so I think I am close to a solution.
Is it correct? And if so, how can I fix it forceNotNull
to work in general?
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Not sure if this is the best method, but this works:
fun splitCSV(s : String) : Array<String> {
return ( s.split(",") as? Array<String>? ).sure() ;
}
While IntelliJ highlights as?
with "This spell will never succeed" ... So my initial optimism fades away
Oddly enough, it looks like it works ...
Like:
fun splitCSV(s : String) : Array<String> {
return s.split(",").sure() as Array<String> ;
}
But with the same warning ... I'm confused, so I'll stop now: - /
Edit
You can of course make it work with List<String>
:
import java.util.List
fun splitCSV(s : String) : List<String> {
return s.split(",")!!.map<String?,String> { it!! }
}
but that's not the question :-)
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