confusion with onExceptionResumeNext passing a observable as a lambda expression - kotlin

Question

io.reactivex.rxjava2:rxjava:2.1.13
kotlin_version = '1.2.30'
I have the following Observable and I am trying to throw an exception to test the capture of the exception in OnError. However, when I pass in the following to the onExceptionResumeNext(Observable.just(10)) I get the following output:
1
2
10
onComplete
fun main(args: Array<String>) {
Observable.fromArray(1, 2, 0, 4, 5, 6)
.doOnNext {
if (it == 0) {
throw RuntimeException("Exception on 0")
}
}
.onExceptionResumeNext(Observable.just(10))
.subscribe(
{
println(it)
},
{
println("onError ${it.message}")
},
{
println("onComplete")
} )
}
However, If I pass a lambda expression to that method I get the following output:
1
2
Observable.fromArray(1, 2, 0, 4, 5, 6)
.doOnNext {
if (it == 0) {
throw RuntimeException("Exception on 0")
}
}
.onExceptionResumeNext { Observable.just(10) }
.subscribe(
{
println(it)
},
{
println("onError ${it.message}")
},
{
println("onComplete")
} )
}
Just wondering what is the difference between doing this onExceptionResumeNext(Observable.just(10)) and doing this onExceptionResumeNext { Observable.just(10) }
Many thanks in advance

Answer 1

in the first case you passing observable to onExceptionResumeNext
in case of error in original observable, you'll be resubscribed to observable that is passed to onExceptionResumeNext
that's why you're getting "1" and "2" from original source and then "10" and "onComplete" from Observable.just(10)
in second case, you're using lambda syntax, so you're effectively doing this:
.onExceptionResumeNext(object : ObservableSource {
void subscribe(#NonNull Observer<? super T> observer) {
Observable.just(10)
}
})
as you can see, observer that is passed to you is not getting subscribed. Thus, nothing is emmited after "1" and "2" from initial source
what you should be doing is
.onExceptionResumeNext { observer ->
Observable.just(10).subscribe(observer)
}