Kotlin Extension Function on Observable<T>.subscribe does not work

Question

I'm trying to write an extension function for Observable.subscribe which automatically logs errors.

fun <T> Observable<T>.subscribeAndLogE(onNext: Consumer<in T>): Disposable =
    subscribe(onNext, ErrorConsumer())

The ErrorConsumer works and presumably logs the error, but subscribeAndLogE does not accept lambdas like .subscribe() does.

observer.subscribe { 
                //works
           }

observer.subscribeAndLogE { 
                //does not work
           }

It says:

With that OnboardingScreen being whichever value T would normally be.

I don't see the original Consumer<in T> in Observable doing anything special to accept lambdas. What am I doing wrong here?

Answer 1

You are passing a parameter of type Consumer to the function. You need to pass a function for the lambda syntax to work. This would work the way you want to:

fun <T> Observable<T>.subscribeAndLogE(onNext: (it : T) -> Unit): Disposable =
        subscribe({ onNext(it) },{ throwable -> Log(throwable) })

and use it like so:

observer.subscribeAndLogE { 
                //works
           }