I have a two level hierarchy with a root and one or more chi

Question

I have a two level hierarchy with a root and one or more children Each of these children have a list of elements they need to track and I d like also to have somehow a root list in the root that incorporates all the children lists Is there a easy stdlib way to have just the root list and then each child simply manages a subset view of this list removing adding Ps no synch problems everything is serial

elect · Answer

something in the direction of `subList` <https stackoverflow com questions 57240799 difference |here> but I guess if the root or the first child modifies the list then I have to update indices for all the other children

ephemient · Answer

if the children are immutable sure if they are mutable you will have to define your requirements more specifically

ephemient · Answer

```val child = object AbstractCollection override val size get = root count isChild override fun iterator = root filter isChild iterator ```

elect · Answer

each child has a consequential view on the root list ie the first 0 10 the secon 11 40 etc

Michael de Kaste · Answer

I had the same issue when I had some sealed class which was viewed by the root and the implementations managed by its children depending on your usage combination root view child view root view child mutate root mutate child mutate root mutate child view there are different solutions if you have root view and child mutate you can simply have root be a value that on every request returns a new list based on the children You can make it better by defining your own concatenation iterator

elect · Answer

i have the worst I guess root mutate child mutate

Michael de Kaste · Answer

what needs to happen when root adds Just add it to the final sublist

elect · Answer

yep

elect · Answer

atm I m leaning toward a `map lt name ArrayList gt ` on the root containing the corresponding children lists and then forwarding the methods I need

ephemient · Answer

if the root exposes a MutableList you ll have to figure out what to do with insertions and removals at any index and before or after any listiterator

ephemient · Answer

if it s a MutableCollection then you only have to figure out what to with removals before any mutableiterator and additions to the whole collection

nkiesel · Answer

do I understand correctly that each child is defined as an index range of the root list Thus a list of items and a list or map if children are not identified by index of IntRange would do the trick