What's the difference between the type `(T) -> ...

# getting-started

[melody]

What's the difference between the type (T) -> Unit and the type Consumer<in T> for function parameters? When I use the first I get a lengthy error with the foo(...) { t: T -> ... } implementation, but the second works just fine.

[homchom]

(T) -> Unit uses Kotlin’s function type syntax and exists on all platforms, whereas Consumer<in T> uses the Java standard library. In general you should always use the former, but I use Consumer<in T> sometimes for legacy functions that are meant to be called from Java code (otherwise you’d have to explicitly return Unit.INSTANCE ).

I don’t know what would be causing such an error from Kotlin; if you want, could you post it here?

[melody]

Sure! I have the following definition in one project:

data class MelodiaGUIItem(..., val clickFunc: (InventoryClickEvent) -> Unit)

And I use it as such in another project:

MelodiaGUIItem(...) { e: InventoryClickEvent -> e.whoClicked.sendMessage("Greenhouse") }

I have linked the projects together correctly as everything else I've been able to use just fine, however when I try this I get the following error:
[T]he class loader 'ScovillePlugin-1.0-SNAPSHOT-all.jar' @253c7e22 of the current class, dev/meluhdy/scovilleplugin/gui/pk/PkGUI, and the class loader 'Melodia-1.0-SNAPSHOT-all.jar' @119fc272 for the method's defining class, dev/meluhdy/melodia/gui/MelodiaGUIItem, have different Class objects for the type kotlin/jvm/functions/Function1 used in the signature

[melody]

I've made sure the kotlin and gradle versions for both projects are the same, so I'm confused why it's saying they have different class objects for a built-in

[melody]

@homchom Just a bump in case you haven't seen; it's alright if this is too old though, but I still haven't figured out why the former doesn't work. Thanks for the clarification between the two though!