kotlinlang #announcements

Hello everyone. I just heard about Kotlin yesterday! I've always been scared of Java and Android.. But the rush of this new language makes me want to learn it.. My question is if it's possible to become a Kotlin and Android programmer without learning Java first? I'm a Python Programmer

6 replies · 3 participants

xantier

05/22/2017, 8:45 AM

but honestly it will be very hard. The ecosystem is still Java and that is a big part of any language

2 replies · 2 participants

faraxraxeed

05/22/2017, 8:47 AM

hi everyone. i have 2 years experience with java android should i move to kotlin ? any reviews for kotlin ?

1 reply · 2 participants

mg6maciej

05/22/2017, 1:07 PM

package `in`.xyz

👍 2

6 replies · 3 participants

igoticecream

05/22/2017, 5:19 PM

Hello, there is something I haven't figured out of the language. Why would I prefer a "regular" extension function over an inlined one? I have read inline has better performance because it basically copy paste the code

3 replies · 2 participants

ikon

05/22/2017, 7:07 PM

What are some good open source Kotlin projects that use the language well?

👍 2

7 replies · 5 participants

Dmitry Kandalov

05/22/2017, 11:12 PM

Or maybe source code 🙂 https://github.com/JetBrains/kotlin/blob/1ab003c029c4476319754df931536cffd518b004/core/descriptors/src/org/jetbrains/kotlin/util/modifierChecks.kt#L177

2 replies · 2 participants

kevinherron

05/23/2017, 2:49 AM

@orangy what’s up with squash vs Exposed?

1 reply · 2 participants

ssp

05/23/2017, 3:52 AM

I build kotlin js project using maven. I set metaInfo flag in pom.xml, but jar is empty. I cannot build dependent project. What am I doing wrong?

8 replies · 2 participants

kiku

05/23/2017, 1:35 PM

is there a tool that can print out the inferred types for variables?

12 replies · 2 participants

vlastachu

05/23/2017, 1:48 PM

Hello, I tried write helper function for application 1 or more optional args on function:

fun <A, B> ((A)->B).optionalApply(optional: A?): B? {
    return optional?.let(this) // "let" good for 1 arg 
}
// test
fun testfun1(i: Int) = i + 1
testfun1.optionalApply(null) // "Function invocation expected" on "testfun1"

4 replies · 2 participants

diesieben07

05/23/2017, 8:48 PM

This is one of the only things I dislike about Kotlin: The bitwise "operators"

4 replies · 3 participants

yperess

05/23/2017, 10:03 PM

Does anyone know of a good guide for kotlin+Dagger in Android? Specifically is like to initialize an object's fields using injection to make mocking in tests easier.

3 replies · 2 participants

mikehearn

05/23/2017, 10:59 PM

This morning the startup I work for announced that we'd raised $107 million in funding from over 40 different banks, financial firms and Intel. At the start of 2016 we didn't have a codebase, Kotlin had not reached v1.0 yet, and we had (and still have) competitors that had all been in development much longer. We have since been able to catch up and become a primary player in the market despite having a far smaller team and far less money to spend until now than those competitors. We are winning conservative bank developers to our platform and although Java is a first class language for us they often choose to use Kotlin too, despite it being optional. I am convinced that a big part of the reason we were able to do that is that we built on Kotlin and the JVM, whereas other platforms did not, and this extra productivity and developer enjoyment has turned directly into success for us.

🎉 20

👍 5

:kotlin-flag: 15

5 replies · 2 participants

gjesse

05/24/2017, 1:49 AM

Yeah null safe types really renders optionals obsolete. Best I can suggest is an 'orNull' or unwrap extension function

2 replies · 2 participants

brett.wooldridge

05/24/2017, 6:24 AM

I expected that a Map is a Map, and the

in

operator would be consistently interpreted as

containsKey(..)

. The fact that it does not cost me over an hour of debugging, and I think is a surprising result for users. I would expect to be able to switch a collection between

HashMap

ConcurrentHashMap

, ... any

Map

and have the code behave consistently.

14 replies · 3 participants

kevin_abrioux

05/24/2017, 8:58 AM

Coucou tout le monde 🇫🇷

🇫🇷 3

1 reply · 2 participants

serandel

05/24/2017, 11:54 AM

https://en.paradigmadigital.com/dev/kotlin-just-another-trend-spoiler-no/

25 replies · 3 participants

maciekjanusz

05/24/2017, 12:21 PM

hello, I'm looking for some insight about sharing kotlin libs between different target platforms, is it even possible for all cases to have unified lib that could be used on all targets?

2 replies · 2 participants

poohbar

05/24/2017, 12:22 PM

val nejkulaťoulinkatějšíKolečko = Circle(5f, 5f, 10f)

🇨🇿 4

🕶️ 2

18 replies · 5 participants

brandon

05/24/2017, 4:17 PM

because the classes don’t exist

2 replies · 2 participants

rook

05/24/2017, 5:08 PM

Does elvis operator work with boolean checks? I currently have

remote.foo != null && remote.foo != local.foo

I’m trying to simplify it to something like

remote.foo != local.foo ?: false

but it seems like the elvis operator can’t be used that way

7 replies · 2 participants

wjur

05/24/2017, 6:47 PM

Hello everybody!

👋 6

1 reply · 2 participants

deinspanjer

05/24/2017, 7:41 PM

println("getMember($name)")
        when (name) {
            "toString" -> return { obj.toString() }
            "valueOf" -> return {
                when (obj) {
                    is JsonNull -> null
                    is JsonArray -> obj.toString()
                    is JsonPrimitive ->
                        if (obj.isNumber) obj.asNumber
                        else if (obj.isBoolean) obj.asBoolean
                        else obj.asString
                    else -> obj.toString()
                }
            }
            else -> {
                try {
                    return obj[name!!]
                } catch (e: NoSuchElementException) {
                    return null
                }
            }
        }

14 replies · 2 participants

mg6maciej

05/24/2017, 9:18 PM

Like this?

val p = item.p
if (p != null) {
} else {
  executeSomething()
}

3 replies · 2 participants

mg6maciej

05/24/2017, 9:26 PM

I claim if you assign it to local

val

before

if

like in my original solution, you will get smart casting.

➕ 1

1 reply · 2 participants

amiracam

05/25/2017, 10:59 AM

@Ruckus interesting 🙂 Smalltalk does this: aBooleanCondition ifTrue: [do true stuff] ifFalse: [do false stuff]

2 replies · 2 participants

wjur

05/25/2017, 1:16 PM

I have a method that accepts java.lang.reflect.Method and I'm trying to check whether the method is returning a nullable type or not (via 'kotlinFunction.returnType.isMarkedNullable'). However, for data classes, there are the componentX() methods and the corresponding getter methods, getXXX(). Interestingly for getter functions there is no kotlinFunction.

16 replies · 2 participants

Title

wjur

05/25/2017, 1:16 PM

diesieben07

05/25/2017, 1:25 PM

wjur: Kotlin does not really see those as functions, they are part of the property. So they are a

KProperty

, not a

KFunction

wjur

05/25/2017, 1:32 PM

I see. Anyway I need to link a getter with a property 😞

I'm writing a module for jackson.

The

JsonProperty

annotation has a

required

property, which defaults to

false

diesieben07

05/25/2017, 1:35 PM

Not sure I am following you, what do you mean by "link"?

wjur

05/25/2017, 1:36 PM

In Kotlin and data classes, this makes a little sense, because it is

isMarkedNullable

that defines whether the property is required or not.

Consider a sample json model:

data class Model(
    @JsonProperty("name")
    val name: String
)

The property says that name is an optional field

while the field is required because is of a non nullable type

diesieben07

05/25/2017, 1:39 PM

Ok, so, you want to go from the java.lang.reflect.Method for the getter to the corresponding KProperty?

wjur

05/25/2017, 1:40 PM

Yes

diesieben07

05/25/2017, 1:42 PM

Since there is only a way to go from Kotlin reflection to Java reflection you have to get all the properties in the class and search through them until

property.getter.javaMethod == yourMethod

wjur

05/25/2017, 1:44 PM

It's working!

You saved The World!

Thank you so much!

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