hmm, playing around with some magic syntax, I'm using JNA and I've got it to the point where thsi compiles and runs:

interface MyFortranCode: com.sun.jna.Library {
  fun start(featureIndex: Int): Boolean
  fun end(featureIndex: Int): Boolean

  companion object: MyFortranCode by LibraryLoader.load<MyFortranCode>()
}

too much magic?

but I think it sorta defeats the purpose of an interface right?

one of the uses we have for said interface is as a shim to allow mock object creation, such mock object creation would then load the live .dll/.so even if we didnt use it.

companion object by lazy { LibLoader.load<...>() }

?

now thats a lot of magic.

also it doesnt compile 😛

yup, its neat, but useless.

companion object: Something by somethingelse

is pretty powerful though

Hey guys, got a question about filtering on collections. Let’s say I have a list that I will filter down based on some criteria and process only a subset of elements:

val myList = List<MyClass>(...)
myList.filter(it.date > cutoffDate)
    .filter(it.type != "excludedType")
    .forEach {
        // process the subset that went through the filters
        ...
    }

For those elements that got filtered out in the above example, I also want to log them (say by sending a message to an outside listener to ack that I got this element but it failed the filter). How do I do that in an idiomatic way?

Try:

.filter {
   val conditionMet = it.type != "excludedType"
   if (!conditionMet) log()
   conditionMet
}

you could also partition the list and act on both resulting lists independently

but that may not be as efficient

If you really wanna make it idiomatic you could write your own

filterOrLog()

extension method that does what I put above, but honestly if this is your only use case I think it's okay.

Asked this earlier but didn't get a response...

Have a look at timber

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hey guys I know this isn't really Kotlin specific, but is there any danger in adding values to a MutableSet in one thread, and reading values in another thread?

Pretty sure your reading thread is going to get a

ConcurrentModificationException

at some point…

hmm true, guess I'll have to use a ConcurrentHashMap

You should try using coroutines and have them communicate through a

Channel

.

the limitation to remove item from mutable map while iterating is the same in kotlin as java, right?

ConcurrentModificationException

- do I have to use iterator?

Yes, you have to use the

Iterator

if you want to remove while iterating.

thanks

Hi all, Just found a quirk that has got me scratching my head. Why should the above code produce different outputs (i.e. select a different case in the when statement) depending on how the

test

value is handled?

yeah I'm thinking of using an

actor

@marstran

@andyb Doesn't happen for me, prints "I have a value" twice...