kotlinlang #getting-started

val itemClickListener: (City) -> Unit = {...}
val cityInfoClickListener: (City) -> Unit = {...}

CitiesAdapter(getCities(), itemClickListener, cityInfoClickListener)

kingsley

11/04/2016, 12:28 PM

Or just go the good old way of

adapter.itemClickListener = ...

when there are a lot of them

bts.rybicki

11/04/2016, 12:29 PM

yep its something I did, I didnt write the entrie funcion in the constructor 🙂

bts.rybicki

11/04/2016, 12:29 PM

but header of the adapter gets kind of big

bamdmux

11/04/2016, 12:29 PM

@bts.rybicki Do you use Rx?

bts.rybicki

11/04/2016, 12:29 PM

and I dont like to pass to many arguments in functions/adapters

bts.rybicki

11/04/2016, 12:30 PM

unfortunately not in this project, but I was thinking about using a bus here (its already used)

defhlt

11/04/2016, 12:33 PM

instead of empty lambda you can also specify a nullable lambda argument e.g.

listener: ((City) -> Unit)? = null

bamdmux

11/04/2016, 12:33 PM

@bts.rybicki Ok, allthough I don't use a bus, just a couple of RxRelays to which I subscribe

kingsley

11/04/2016, 12:34 PM

@bts.rybicki why not. You can just break the header into multiple lines

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class CitiesAdapter(
  val cities: List<City>, 
  val itemClickListener: (City) -> Unit,
  val cityInfoClickListener: (City) -> Unit,
 ...
)

bts.rybicki

11/04/2016, 12:34 PM

I know, I know : )

bts.rybicki

11/04/2016, 12:35 PM

maybe thats not that bad after all

🙂 1

adambl4

11/04/2016, 12:35 PM

typealias CityClickListener = (City) -> Unit

bamdmux

11/04/2016, 12:36 PM

Or you can have a public method like

addClickListener {whatever()}

instead of using the constructors if that suits you better

bts.rybicki

11/04/2016, 12:38 PM

yep, I know, Ill choose best way that fits me, thanks for your time guys

mbstavola

11/04/2016, 5:52 PM

Is there a short hand for this?

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foo.filter {
  !bar.contains(it)
}

Basically, all the items in Set A that do not appear in Set B. I was pretty sure there was a functional extension for this, but I can't seem to find it.

mbstavola

11/04/2016, 6:11 PM

I see that Collection has minus(), which is exactly what I need

oshai

11/04/2016, 9:33 PM

I am trying to make this code less verbose:

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return when {
            currentCellState == Alive && liveNeighbours < 2 -> Dead
            currentCellState == Alive && liveNeighbours >= 2 && liveNeighbours <= 3 -> Alive
            currentCellState == Alive && liveNeighbours > 3 -> Dead
            currentCellState == Dead && liveNeighbours == 3 -> Alive
            else -> Dead
        }

oshai

11/04/2016, 9:34 PM

should I do something like

when Pair(currentCellState,  liveNeighbours) { ..

? Any other idea?

cedric

11/04/2016, 10:05 PM

If performance is an issue, you could have a

Map<Pair<State, NeighborCount>, State>

and fill it with

(Alive, 0) -> Dead

(Alive, 1) -> Dead

, etc… up to 8 neighbors

cedric

11/04/2016, 10:05 PM

constant time look up

cedric

11/04/2016, 10:06 PM

Not sure it would be faster than the

if

above though

cedric

11/04/2016, 10:08 PM

You can go closer to the metal by replacing pairs by numbers and put this in an array

kqr

11/05/2016, 7:00 AM

@richodemus yes, but I cant imagine use case where I would need all classes except some.

orangy

11/05/2016, 10:05 AM

@cedric I don’t think map lookup, even if constant, will be better than couple of conditions.

orangy

11/05/2016, 10:16 AM

@oshai I would just make it nested when statements. Like

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when(currentCellState) { 
    Alive -> when(liveNeighbours) {
       in 2..3 -> Alive
       else -> Dead       
    }
    Dead -> when(liveNeighbours) {
        3 -> Alive
        else -> Dead 
    }
}

oshai

11/05/2016, 10:53 AM

thanks @orangy