Hi All, I want to create extension function (like `run` <https://kotlinlang.org/api/latest/jvm/stdli...

# announcements

[aerialist]

Hi All,
I want to create extension function (like run https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/run.html) which returns nothing (Unit) (see code block).

towards function purpose: run block() in scope of T. And if block() returns some result - it must be ignored.

Kotlin-Dev Team, could you please recommend better name? And do you have plans to add same extension to language?
Thank you in advance.

-.rb

[diesieben07]

Already exists, it's called run.

[aerialist]

No, it returns a result
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/run.html

[natpryce]

If your block returns Unit, then run returns Unit, which (in Kotlin) is the same as returning no value.

[natpryce]

E.g. your towards function will return Unit. If you don’t explicitly declare a result type of a block-structured function, Kotlin defaults the result type to Unit.

[aerialist]

I know. I'm talking about solution without conditions. Yes, I need Unit

[natpryce]

You mean you want to be able to pass in a block that would return non-Unit if passed to run, and force the result of the towards function to be Unit regardless?

[aerialist]

towards function purpose: run block() in scope of T. And if block() returns some result - it must be ignored.

[natpryce]

👍

[natpryce]

Q: is there a reason why this is required, instead of just ignoring the result of run?

[natpryce]

E.g. reflection or static code analysis or somesuch

[aerialist]

Simple - additional protection. No return-value - no problems with it 🙂

[alllex]

function purpose: run block() in scope of T. And if block() returns some result - it must be ignored.

@aerialist It looks like you are giving a definition of a side-effect . So maybe try to think in that direction: effect or affect(ed), or runEffect, etc.

[natpryce]

It’s convention to use also or apply for side effects. The apply extension method also discards any result from the block.

[natpryce]

Maybe that’s good enough?

[aerialist]

No, because in case of apply I can continue my work with object. In apply docs: "... and returns this value."
In case of towards I have nothing to return and my work with object is finished.