there are probably more primitive types that i am missing

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ok i think i can successfully create instances of inner classes now, however this does not work if security manager is active

class A {
    inner class B {
        inner class C {
            var empty: Int = 0
        }

        var empty: Int = 0
        var a: MutableList<C>

        init {
            a = mutableListOf(C())
        }
    }

    var a: MutableList<B>

    init {
        a = mutableListOf(B())
    }

    /**
     * test variable
     */
    var empty: Int = 0
}

fun getDeclaringUpperLevelClassObject(objectA: Any?): Any? {
    if (objectA == null) {
        return null
    }
    val cls = objectA.javaClass ?: return objectA
    val outerCls = cls.enclosingClass
        ?: // this is top-level class
        return objectA
    // get outer class object
    var outerObj: Any? = null
    try {
        val fields = cls.declaredFields
        for (field in fields) {
            if (field != null && field.type === outerCls
                && field.name != null && field.name.startsWith("this$")
            ) {
                /*
                `field.isAccessible = true` does not work with a Security Manager
                java.security.AccessControlException: access denied
                ("java.lang.reflect.ReflectPermission" "suppressAccessChecks")
                */
                field.isAccessible = true
                outerObj = field.get(objectA)
                break
            }
        }
    } catch (e: Exception) {
        e.printStackTrace()
    }

    return outerObj
}

/**
 * returns a [MutableList] of classes parenting the current class
 *
 * the top most class is always the last index
 *
 * the last class is always the first index
 *
 * for example: up(f[0].a[0].a[0]) = 0(f[0].a[0].a[0]) 1(f[0].a[0]) 2(f[0])
 */
fun up(a: Any, m: MutableList<Any> = mutableListOf(), debug: Boolean = false): MutableList<Any> {
    m.add(a)
    if (debug) println("get upper class of ${a.javaClass.name}")
    val upperC = getDeclaringUpperLevelClassObject(a)
    if (upperC == null) abort("upperC is null o.o")
    if (a.equals(upperC)) return m
    else {
        return up(upperC, m)
    }
}

/**
 * use as follows: `instanceChain(`[up]`(f[0]))`
 */
fun instanceChain(chain: MutableList<Any>, index: Int = chain.lastIndex, debug: Boolean = false): Any {
    return if (index == 0) {
        chain[index]
    } else {
        if (debug) println("chain[$index] = " + chain[index])
        val outer = chain[index]
        val toRun = Class.forName(chain[index].javaClass.name + "$" + chain[index - 1].javaClass.simpleName)
        val ctor = toRun.getDeclaredConstructor(chain[index]::class.java)
        val lowerCInstance = ctor.newInstance(outer)
        if (debug) println("lowerCInstance = " + lowerCInstance!!::class.java)
        if (index == 1) lowerCInstance
        else instanceChain(chain, index - 1)
    }
}

fun Test() {
    val f = mutableListOf<A>()
    f.add(A()) // this is required, i do not know how to do accomplish this in the init block
    println("f[0] = ${instanceChain(up(f[0]))}")
    println("f[0].a[0] = ${instanceChain(up(f[0].a[0]))}")
    println("f[0].a[0].a[0] = ${instanceChain(up(f[0].a[0].a[0]))}")
    abort()
}

Say I've got a World class. A world can contain Spheres, and a Sphere can have properties such as Colour. So on my World class I have a factory function within a companion object called defaultWorld. This returns me an instance of a World with two Colour.RED Spheres. What's the best way of taking a defaultWorld and modifying it so that, for example, one of the Sphere's is Colour.BLUE not RED ? At the moment all the attributes of Sphere are val's not vars, so I can't just do world.spheres[0].colour=Colour.BLUE. And even if I did change it to var, that changes the defaultWorld for everything. So what's the best way of having some sort of template object that I can easily create new variants from ?

Unrelated question. How is

MutableList

both an interface and a class in the stdlib without their names clashing? Do they have separate jvmNames?

if I have a

Map<String, Thing?>

is there an equivalent of

Iterable#filterNoNull()

that will give me a

Map<String,Thing>

for all non-null values?

like say I have this

var mileageValuesToYears = mapOf(
    1980 to 900000,
    1981 to 900000,
    1982 to 100000,
    1983 to 120000
)

Hello guys , does anyone have nice tutorials or articles to start with annotation processing

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I just joined this group and I have a question about Testing frameworks in Kotlin. I find Spock's data driven testing very useful and was wondering if there was anything similar to that in Kotlin frameworks? I have checked out Spek, but found its data driven testing (parameterised) to be too restrictive and verbose

is it “hacky” to use ::isInitialized?

Hi, I’m porting a fairly large Kotlin codebase to run under Java 9/10/11 (in a first instance just being compatible with Java 9 modules using classpath/UNNAMED-MODULE), but am hitting some fairly basic obstacles with the Kotlin compiler. Please reply if you have any experience in this area.

what’s the default/suggested/safest/recommended way to initialize stuff like this ? http://snpy.in/kISHVt

is it at all possible to type anonymous objects dynamically? i’m trying to do something like this:

fun reportError(errorState: ErrorState) {
    val type = object : Exception {
         type.className = errorState.className
    }
    silentlyReportException(type)
    handleDifferentErrorStates(errorState)
}

Can I reuse the constructor signature of a superclass, so that I don't have to re-type all the arguments of the constructor?

open class SuperClass(val foo: String, val bar: String) {}
open class SubClass : SuperClass {}
val instance = SubClass(foo = "hello", bar = "world") // <-- subclass has same constructor signature as superclass without needing to re-type the signature in SubClass's declaration

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how do i pass a vararg to a vararg

eg,

fun String?.tokenizeVararg(vararg delimiters: String, returnDelimiters: Boolean = false): List<String>? {
    return if (this == null) null
    else this.tokenizeVararg(delimiters = delimiters, returnDelimiters = returnDelimiters)
}

Assigning single elements to varargs in named form is forbidden
Type mismatch: inferred type is Array<out String> but String was expected

how do i compare

Number

for example

fun Number.comparisionsGreaterThan(i: Number): Boolean {
    return this < i
}

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Ask, Suggest where fundamental learning kotlin?

hey guys, i have list A and list B, I want to go over B and set some property inside A depending on what I find in B, I wanna do this without 2 literal loops

Or rather, what would be an idiomatic way to describe some expectations that need to be fulfilled in the test, within a certain timeout?

Can I always use Kotlin's Object instead of usual structure of getting Singleton in Java? http://prntscr.com/nfb8xr Or it can bring some problem? for example in time working in different threads.

Would somebody please help me understand what is happening with a function declaration like the following?

fun foo(): String = "bar"

What I understand is that function foo takes no parameters and has a return type of String. What is odd to me coming from other languages where I have never seen this, is that it is valid for there to be no body declaration but just an equal sign after the return type assigning the return value as a constant. If you could, would you please provide a use case for a function declared similarly?

Does

mapOf

have any form that tapes type parameters? Like

mapOf<String, Int>(...)

?

is there a more idiomatic way in kotlin to write sth. like this?

while (true) {
    val rows = repo.findAll(page)

    if (rows.isEmpty()) {
        break
    }

    doSomething(rows)
}

I have an enum which is defined in Java and has the property name, which is a string. now when I try to fetch this I get an Overload resolution ambiguity error, because Kotlin itself -also- defines name as a String, how do I access .name from the original enum class now? (Without using reflections)

what's the difference between the data class code and the java code presented?