https://kotlinlang.org logo
Channels
Powered by
#announcements
  • m

    mfulton26

    02/14/2017, 9:56 PM
    But I wonder why 
    var port = -1
    wouldn't suffice (it would be cheaper than a delegate property).
  • a

    artem_zin

    02/14/2017, 10:08 PM
    @sdeleuze the thing is that 
    lateinit
    uses 
    null
    as “not-initialized”, at the same time 
    Int
    will be interpreted as primitive java 
    int
    whenever possible to avoid allocation on heap, that means that combination of any primitive types with 
    lateinit
    is not possible because 
    lateinit
    needs reference type (for 
    null
    ) but primitives are not reference types… We’re facing it from time to time and have to fallback to 
    Delegates.notNull()
    as suggested before, you can vote for IDE quickfix for that https://youtrack.jetbrains.com/issue/KT-12515
  • a

    artem_zin

    02/14/2017, 10:10 PM
    But I wonder why 
    var port = -1
    wouldn't suffice (it would be cheaper than a delegate property).
    Because 
    -1
    can be valid initialized value for your business logic.
  • s

    sreich

    02/14/2017, 10:12 PM
    i guess port is a bad example then
  • a

    artem_zin

    02/14/2017, 10:15 PM
    Ah, my bad, I read it as if 
    -1
    will be used as “not-initialized” state by 
    lateinit
    internally, surely you can use some default value if possible, but beauty of 
    lateinit
    is that it removes 
    if (initialized)
    checks from your code
  • s

    sreich

    02/14/2017, 10:16 PM
    @sdeleuze shouldn't port just default to some default port?
  • a

    aimozg

    02/14/2017, 10:18 PM
    if 
    port
    could be "non-initialized", why not make it 
    Int?
  • s

    sreich

    02/14/2017, 10:25 PM
    Yeah.. Which means you can't have lateinit (for good reasons)
  • s

    sdeleuze

    02/14/2017, 10:27 PM
    Yeah 
    @LocalServerPort var port: Int? = null
    is probably the right solution
  • a

    aimozg

    02/14/2017, 10:27 PM
    It depends though how you want to interact with field. Nullable means "could be non-initialized and I have to check/suppress in calling code", 
    lateinit
    is "could be non-initialized but I want to work with it as if it was always initialized with background checks if necessary"
  • s

    sdeleuze

    02/14/2017, 10:27 PM
    In my use case I just use it in String interpolation
  • a

    aimozg

    02/14/2017, 10:27 PM
    and sensible/unsensible default is "I promise I'll initialize it somewhere"
  • s

    sdeleuze

    02/14/2017, 10:28 PM
    And it seems to be ok with 
    Int?
  • m

    mfulton26

    02/14/2017, 10:28 PM
    @User uploaded a file: BoxedPrimitiveLateInitDemo and commented: Interestingly enough Kotlin does support 
    lateinit
    for boxed-primitives via generics but simply doesn't have the grammar to directly express it.
    BoxedPrimitiveLateInitDemo.kt
  • a

    aimozg

    02/14/2017, 10:29 PM
    yeah, there was even a somewhat-related bug when the compiler couldn't properly distinguish Java 
    @NotNull Integer
    and 
    int
  • p

    Paul Woitaschek

    02/14/2017, 10:50 PM
    Is there a kotlin-way for the listener ceremony? Like that having the list of listeners, a method for adding, a method for removing and iterating over all listeners upon a event?
  • r

    Rob

    02/14/2017, 11:56 PM
    I got my kotlin book in the mail!!!
  • s

    sreich

    02/15/2017, 12:05 AM
    (without the lazy it would be assigned the moment the class is created, which is before the context is created, it seems)
  • p

    poohbar

    02/15/2017, 2:45 AM
    i want to add 
    square
    to the 
    Math
    standard Java class
  • p

    poohbar

    02/15/2017, 2:45 AM
    I did:
    Copy code
    fun Math.square(a: Double) = Math.pow(a, 2.0)
  • p

    poohbar

    02/15/2017, 2:45 AM
    but I can not call it even though the definition can be compiled
  • p

    pniederw

    02/15/2017, 2:53 AM
    @poohbar you are adding an instance method here. Adding a companion (static) method to a class written in Java is not currently supported.
  • p

    poohbar

    02/15/2017, 3:09 AM
    ok..
  • p

    poohbar

    02/15/2017, 3:10 AM
    is destructuring in lambda also not supported?
    Copy code
    val myLambda = { (x, y), z ->
   println(x,y,z)
}
  • p

    pniederw

    02/15/2017, 3:50 AM
    @poohbar this should be supported in 1.1
  • p

    pniederw

    02/15/2017, 3:53 AM
    Copy code
    val myLambda: (Pair<Int, Int>, String) -> Unit = { (x, y), z ->
  println(x)
  println(y)
  println(z)
}
  • m

    mg6maciej

    02/15/2017, 9:33 AM
    Is this 1.1 or did I just not see it before? 
    BiFunction(::aFunc)
    where 
    BiFunction
    is SAM, interface is Java and 
    aFunc
    is just a top-level function.
  • k

    kirillrakhman

    02/15/2017, 9:36 AM
    it's just SAM conversion
  • k

    kirillrakhman

    02/15/2017, 9:36 AM
    because 
    BiFunction
    is a SAM, a synthetic constructor that takes a lambda is generated.
  • m

    mg6maciej

    02/15/2017, 9:37 AM
    Yeah, but I was used to 
    BiFunction { a, b -> aFunc(a, b) }
    .
1...729730731...3338Latest