Hi What is this feature called in Kotlin, where we call a function with :: ?

```fun someFunction(param: (String) -> Unit) {}

class SomeClass {
    fun functionWithOneParameter(param: String) {}
}

// caller place
// what is this :: notation called?
val someClass = SomeClass()
someFunction(param = someClass::functionWithOneParameter)

probably ‘callable reference’ https://kotlinlang.org/docs/reflection.html#callable-references

Thank you

And just to make it clear, you are not calling the function where you reference it with

::

. 🙂

So we are just passing the reference and not actually calling it? Now I wonder if there is any performance difference or some other difference when reference with

::

and actually calling the function?

It's not so much about performance, it is simply a different use-case. You can for example give callbacks like that, that are then called on certain events and similar.

Got it, thanks

it can be thought of as syntactically cleaner, because you know for sure that you’re using another method verbatim instead of (possibly) hiding some side effect in a lambda AFAIK the performance is basically equivalent on modern JVMs, or at least not something you should really care about 99% of the time

the call performance is the same

"callable reference" 6 syllables 😬, that's probably why this is called a "tear-off" in other languages.