Hello is it possible to override forEach When we tried the I kotlinlang #announcements

Hello, is it possible to override forEach { } ? When we tried, the IDE at least always redirects to the stdlib, not to the one we implemented on our class. Weird or expected behavior?

Milan Hruban

12/03/2019, 10:57 AM

I don't think you can override extension functions

adimit

12/03/2019, 11:01 AM

You can however just not import the extension function. Remove the

import

statement for your the stdlib

forEach

then import your own

forEach

Overriding extension functions makes no sense, since they're static, and not actually functions that really belong to the class they're extending. BTW, I might add: defining your own

forEach

method on, say,

List<T>

is probably a silly idea. If it does something special, at least reflect that in the name, as people would otherwise be easily confused.

galex

12/03/2019, 11:08 AM

I thought local functions have precedence on extension functions, which is why it’s weird. The use case itself makes sense, it’s on some internal class which is a collection which contains in that special case a collection itself. But yeah, I am still surprised by the fact that defining our own forEach didn’t work

@adimit I think there was no import, surprisingly. Will check that again.

gian

12/03/2019, 11:10 AM

stdlib is imported by default, isn’t it?

Kroppeb

12/03/2019, 11:28 AM

If you are "overriding" for a subclass, then it can only call the extension after your type has been (smart)casted to the subtype. Anyway you could just rename the function

forEachRecursive

, or something similar.

galex

12/03/2019, 11:55 AM

Yup that’s what we ended doing, renamed it

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