I just can't understand why it is possible to extend function type in kotlin ? And then why we can't extend String? then, which is also a type.
interface CustomFunctionType : () -> Unit {
// this is possible, buy how?
}
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abhi
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[`Function
`](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-function.html) is interface and hence open by default. While classes are final by default. – Animesh Sahu May 31 '20 at 14:28 -
so you mean that lambda is also a Function as well. Right ? – abhi May 31 '20 at 14:50
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A lambda is `Function
` in JVM bytecode, you can try to decompile to Java for a better view. For example `(Int) -> Int` is `Function1 – Animesh Sahu May 31 '20 at 14:56` which is `interface Function : Function {...}` again inherited from `Function ` so yeah, this is hierarchy. -
String is a final class. Functional declarations are not final. They are like interfaces, which are never final. – Tenfour04 May 31 '20 at 15:26