i have a mutable list of objects, and a reference ...

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[LastExceed]

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]

Check if this is what you are looking for?

Untitled

[LastExceed]

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

[LastExceed]

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

[LastExceed]

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

[wbertan]

takeUntilItem was my extension

[wbertan]

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

[LastExceed]

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

[wbertan]

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. 🙂