Kotlin lambda syntax confusion

Question

I'm confused by Kotlin lambda syntax.

At first, I have

.subscribe(
          { println(it) }
          , { println(it.message) }
          , { println("completed") }
      )

which works fine.

Then I moved the onNext to another class called GroupRecyclerViewAdapter which implements Action1<ArrayList<Group>>.

.subscribe(
          view.adapter as GroupRecyclerViewAdapter
          , { println(it.message) }
          , { println("completed") }
      )

However, I got the error:

Error:(42, 17) Type mismatch: inferred type is () -> ??? but rx.functions.Action1<kotlin.Throwable!>! was expected
Error:(42, 27) Unresolved reference: it
Error:(43, 17) Type mismatch: inferred type is () -> kotlin.Unit but rx.functions.Action0! was expected

I can fix the error by changing to:

.subscribe(
          view.adapter as GroupRecyclerViewAdapter
          , Action1<kotlin.Throwable> { println(it.message) }
          , Action0 { println("completed") }
      )

Is there a way to write the lambda without specifying a type? (Action1<kotlin.Throwable>, Action0)

Note: subscribe is RxJava method

Edit 1

class GroupRecyclerViewAdapter(private val groups: MutableList<Group>,
                           private val listener: OnListFragmentInteractionListener?) :
RecyclerView.Adapter<GroupRecyclerViewAdapter.ViewHolder>(), Action1<ArrayList<Group>> {

Answer 1

view.adapter as GroupRecyclerViewAdapter part should be lambda func, not Action, since onError and onComplete also lambdas

so, to fix this try:

.subscribe(
          { (view.adapter as GroupRecyclerViewAdapter).call(it) }
          , { println(it.message) }
          , { println("completed") }
      )

with your names (replace Unit with your type)

class GroupRecyclerViewAdapter : Action1<Unit> {
    override fun call(t: Unit?) {
        print ("onNext")
    }
}

with lambdas

val ga = GroupRecyclerViewAdapter()
...subscribe(
    { result -> ga.call(result) },
    { error -> print ("error $error") },
    { print ("completed") })

with actions

...subscribe(
    ga,
    Action1{ error -> print ("error $error") },
    Action0{ print ("completed") })

pick one

Answer 2

You have two versions of the subscribe method to choose from:

• The first (the real one) has the signature subscribe(Action1<ArrayList<Group>>, Action1<Throwable>, Action0).
• The second version is generated by the Kotlin compiler and has the signature subscribe((ArrayList<Group>>) -> Unit, (Throwable) -> Unit, () -> Unit)

In your code, however, you pass the following parameter types:

subscribe(
    view.adapter as GroupRecyclerViewAdapter, // Action1<Throwable>
    { println(it.message) },  // (Throwable) -> Unit
    { println("completed") } // () -> Unit
)

As you can see, these parameter types satisfy none of the available signatures. The other answer gives you some solutions to your problem. In addition, you can make GroupRecyclerViewAdapter implement the functional type Function1<ArrayList<Group>, Unit> (they're interfaces, too) instead of Action1<ArrayList<Group>>.