sure would be nice to have

^

as a power operator

How to properly implement

addListener { ... }

? Java's example shows something like

addListener((obs, oldVal, newVal) -> { ... })

Question on covariance. Container is covariant on T but for this case i ignored out modifier on T and as expected processContainer1 fails at compile time ( required<Number> but found <Int>). Just wondering about processContainer which ensures type safety as well. Is there any reason why "out" would be preferred over T : Number?

class Container< T : Number > (private var value : T ) {
    fun getContainedValue() : T = value
}

fun <T : Number > processContainer( container : Container<T> ) {
    container.getContainedValue()
}

fun processContainer1( container : Container<Number> ) {
    container.getContainedValue()
}

fun main(args: Array<String>) {

    val intContainer = Container(2)

    processContainer( intContainer )
    processContainer1( intContainer )  // Errors
}

Ive got a stupid question. In Room entity (data class) has a primary key id property which is autogenerate. So when inserting I dont want to add the id. If I put a default value on it, kotlin will make me label all the params since it is first. Whats the standard way of takling this, factory method?

I'm using Room on Android and I've replaced AsyncTask with coroutines. It seems to work but I'm wondering if there is a better way than

GlobalScope.launch { dao.insert(note) }

for simple background work where I don't expect a result. Also, would

thread { dao.insert(note) }

be an appropriate alternative?

what is

with

and how do I make use of it?

maybe rename

private Foo foo;

to

private Foo mFoo;

What DSL stands for?

Exactly when I tough i was getting pro at kotlin I fall on the most basic thing... this code below do not compile 🙂 I know about ranges... I can do

in Int.MIN_VALUE until 0

I also know I can save the value and compare to 0 using a

when

with no parameter. But are these really the only ways? Can't I do something similar to the code below? And to check !0 with ranges I would have to write:

!in in 1..Int.MAX_VALUE && !in -1 downTo Int.MIN_VALUE

But this doesn't look right, there must be another way, right?

e.g.

class BasePerson : Person
Interface Person

?

Is it possible to iterate over statements in a block? E.g.

{
  someFun()
  "Some Text"
  anything + else
}

In order to "catch" some specific statements

hello I hav a MutableList of Ints, where each Int is like this: 24 24 25 26 25 26 24 I want this to be coverted to a map with Key being either 24 or 25 and value being the number of 24s. Like this: 24 3 25 2 26 2 Is there an easy function in the library to do that?

I have an java interop question: I have a Kotlin function that accepts vararg argument (i.e.

fun processStrings(vararg strings: String)...

When I try to call it from Java though it’s seen as a function that accepts an array of strings instead of vararg function. Is there a way to make this function accept vararg from Java’s perspective?

hey guys So i hav a base class called Wearable and this class has a member named "name" And i hav another class name ClothTunic and this class inherits the class Wearable plus has a member named "armor" And say for examples sake, a class named PowerRing which inherits the Wearable and has a member named "strenght" So all this wearables are managed by a WearableManager which has a function called getTotalArmor() : Int which returns the total armor from all these wearables tht a entity has. So my question was this: How do i know which Wearable has a "armor" variable or a "strength" variable? How do i do it in Kotlin?

Ok So I hav a class name StrawHat, like this

class StrawHat {
    constructor() : Wearable(name = "Straw Hat") {

    }
}

The constructor of this class gives an error: Expecting a this or super constructor call.... How do i call this type of constructors?

There doesn't seem to be a LinkedList in the Kotlin std library - any obvious alternatives?

hiya, is there any way to quickly get number of decimal digits from

Double

? I would like the exact number of deciaml digits, ie. 424.234 would return 3 or “234” (either would be good) thanks in advance.

And

0b_1100_0000

should just work like that.

This message was deleted.

Does Kotlin have some sort of built-in mechanism to update text files? My task is to read a text file, and parse them line by line. When I match a specific pattern, I want to write a slightly changed line, otherwise the original line. I could implement such a processor myself, but I am wondering if there is already support for that in Kotlin?

fun isFavorite(otherIceCream: IceCream) = iceCream == otherIceCream

What is going on in this syntax? We have one equality operator and another is assignment.

How to read this? val filter = {predicate: (Int) -> Boolean -> {collection: List<Int> -> collection.filter(predicate) }}

Any way to find this: https://stackoverflow.com/questions/52353007/find-kotlin-classes-implementing-an-interface

Is this possible in Kotlin ?

guess i can just use enums or sealed classes instead

i can't be the only one that thinks the constant casting between ints, doubles, etc in arithmetic kinda ruins the beautiful readability of kotlin

This message was deleted.

Hello ! I am trying to understand how to get Contacts (from ContactsContract) using a ViewModel. I only found the official tutorial which uses a CursorLoader (https://developer.android.com/training/contacts-provider/retrieve-names). Are there any tutorials, guides or articles who could help understand how to do that? Thank you for your patience! EDIT: Ignore the question as it wasn't related to Kotlin. EDIT2: If you care, it seems that I was understanding it the wrong way. ContactsContract is a ContentProvider, which is an API on a database. It would be redundant with a Room/DAO implementation.

So I hav a object called BasicSword which is a derived class of MeleeWeapon, and in a object called BasicSoldier i hav some code like this:

object BasicSoldier {
   fun init() {
      this.meleeWeapon = BasicSword
      .....
    }
    lateinit var meleeWeapon : MeleeWeapon

How do i instantiiate the BasicSword object ? It has a fun init() method which is used to instantiate it. Pls help

Hi guys! i'm creating a new project using Kotlin + Spring and Gradle but for some reason i receive this error: