Pass interface as parameter in Kotlin

Question

I want to pass an interface as parameter like this:

class Test {     fun main() {         test({})         // how can I pass here?     }      fun test(handler: Handler) {         // do something     }      interface Handler {         fun onCompleted()     } } 

In Java, I can use anonymous function like test(new Handler() { .......... }), but I can't do this in Kotlin. Anyone know how to do this?

Answer 1

In Kotlin you can do :

test(object: Handler {     override fun onComplete() {      } }) 

Or make a property the same way:

val handler = object: Handler {     override fun onComplete() {      } } 

And, somewhere in code: test(handler)

Answer 2

since your interface has only one function. you can convert it to SAM like this

fun interface Handler {         fun onCompleted() }  

then you can just implement this interface using lambda instead and so reduce the overall written code. this is only possible in v1.4