i have a mutable list of objects and a reference to one of t kotlinlang #announcements

i have a mutable list of objects, and a reference to one of the objects in that list. i want to keep every object from start until (including) the object i have a reference to, and drop everything that comes afterwards. I see countless ways to do this (e.g.

myList.dropLast(myList.size - 1 - myList.indexOf(thatObject))

) but none that really satisfies me in terms of readability. can you guys give me some suggestions? I figured the best way would involve

myList.retainAll()

somehow but i couldnt find a good way to make use of it

wbertan

09/12/2019, 9:18 AM

Check if this is what you are looking for?

Untitled

LastExceed

09/12/2019, 9:24 AM

ah, sorry, its actually an

ObservableList

from TornadoFX which doesn't have a

.takeUntilItem()

function unfortunately. I thought it had the same functions as a normal

MutableList

but apparently not

but otherwise yes,

myList.retainAll(myList.takeUntilItem(thatItem))

would have been what I'm looking for, though I'm still not sure whether thats the best approach as it seems inefficient

oh i also just realized that my original example is incorrect as it returns a new list rather than modifying

myList

wbertan

09/12/2019, 9:35 AM

takeUntilItem

was my extension

list.take(min(list.indexOf(item) + 1, list.size))

LastExceed

09/12/2019, 9:39 AM

oops, im stupid your extension function returns a new list, but i want it to modify the list instead. i found the solution now,

ObservableList

has a function

.remove(from: Int, to: Int): Unit

which is exactly what i need. still, thanks for your help

👍 1

wbertan

09/12/2019, 9:51 AM

no problem, also let me provide an advice, try lay down the cases, as I did with the solution above, in a test file. For me it makes more easy to find a solution, and more confident about it - and about to refactor it. Also helps in identifying corner cases, as the last item, no item, etc. 🙂

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