Hello,please solve the problems.Registration does not work where can be an error ? Thanks https://hastebin.com/punafomaze.cpp

How can I have call site generic in interface property?

interface FooProvider {
    fun <T> getFoo() : T <--- works
    val <T> foo: T <--- doesnt
}

Is this supposed to be valid Kotlin? The compiler can't parse having braces back-to-back like that.

I’m not sure what

masterplanRepository.save()

returns (maybe an instance of the saved record), but if it’s just

Unit

, I might suggest writing

.apply(masterplanRepository::save)

instead

S

is the type of the accumulator (and therefore also the return type).

Is there a easy way to "pretty print" toString of a dataclass (indentations, new lines etc) ?

-- if I rename the class to WhateverViewModel it all works lol

If this will filter my sensorType intArray to return a reduced array where values == 6

val indexes = sensorType.filter { sensorType -> sensorType == 6 }

... how do I instead get an array of the matched indexed positions?

how would you implement this java interface in kotlin if you want the output type to be equivalent of

void

?

public interface RequestHandler<I, O> {
    public O handleRequest(I input, Context context);
}

I tried making

O

a

Nothing

but that wouldn't compile.. I also tried

java.lang.Void

to no avail.

Hi everyone, glad to be here. I am trying to create an extension property, but I want to avoid creating the object that the getter returns every time I am accessing the property. Does anyone have an idea how I can implement that please?

Hello! Can someone tell me why can’t I do this?

quick one: Please, who knows an idiomatic way to select a previous or next element in a collection in Kotlin?

Hey I have an anonymous object structure that I want to take as a parameter in a function, what do I put for the type on the parameter?

I want to have a constructor that takes different parameters, does some computations, and then calls the primary constructor with the result of that computation.

But it looks like that is not possible?

I want to do this:

when(x)
    < 1 -> ...
    in 2..5 -> ...
    6 -> ...
    else -> ... (greater than 6)

I have an abstract parent class A and child classes B and C. I want to declare an abstract method in A such that the implementation in B and C must have a return type of B or C respectively. Is there a way to do this?

got it, i just used a setter/getter

Is there any way to get reified type in a class function?

class Container<T> {
    fun useContainedClassType() {
        T::class.java
    }
}

I have a question on writing kotlin test with JUnit5. Why would a extra module name be added to the test method? This example was running on latest IntelliJ IDEA.

Is it possible to access copy function of data class in Java with optional parameters? e.g I want to change a3 in Java. What is the best way to do it considering my class A is immutable. Should I write setter method which internally should do a copy by updating the required value or is there any other option?

Hey all. I'm new. I was fiddling around with generics and type inference using functional approaches, but I'm a little confused about type inference logic for second order functions. Given

fun <E> firstOrderFnWithSecondOrderTypeInference() = { value: E -> value }

, attempting to

firstOrderFnWithSecondOrderTypeInference()(42)

gives me a type inference error:

Type inference failed: Not enough information to infer parameter E in  fun <E> firstOrderFnWithSecondOrderTypeInference( ) : (E) → E Please specify it explicitly.

firstOrderFnWithSecondOrderTypeInference<Int>()(1234)

works because there's no type inference for

E

of the second rank function. I guess what I'm looking for is a why it's like this so I can understand the language a bit better. I know that C++ is the same way, same with Typescript, so I wonder if there's an underlying reason.

namespacing is (mostly) handled using

package

directives and class names rather than filenames

Is there any ideomatic way to encode a Long into base64 and vise-versa in Kotlin?

how come i can't do list.forEach(println) and i have to do list.forEach(::println)?

This message was deleted.

Coming from Java where nullability is sort of a free for all, I wonder how do you resolve this problem. I have a

User

data class which has a

type

field. The type can be either

REGULAR

or

ADMIN

. When it is of type

ADMIN

the user will always have a not null

companyId

but when it is a

REGULAR

user the

companyId

will always be null. Therefore the

companyId

now has to be nullable and I am forced to handle it even in this case:

val user = db.getUser(id)
if (user.type == ADMIN) {
  // user.companyId is definitely NOT NULL here but the compiler obviously has no idea
} else {
  // user is a REGULAR user so the companyId is null

The only way around this is to have two different classes: an

AdminUser

and

RegularUser

that will reflect the reality more closely. Is there a better way? In Java the compiler does not care and I get no warnings.

What is the most clean way to rewrite this in kotlin

if ( a == null ) {
do something 
} else {
do something else
}