Remove objects at specific indexes from Array in Swift 5

Question

I have an array of dictionaries and another array which contains indexes from which need to be removed from the first array. I tried making them IndexSet and using the removeObjects(at: indexes:IndexSet) but fails. Anyone has any idea how to do this?

print(listArray.count)
print(listToBeRemoved.count)`
let set = NSMutableIndexSet()
for (idx, index) in listToBeRemoved.enumerated(){
     set.add((index as! NSIndexPath).row)
     if idx == listToBeRemoved.count-1{
     listArray.removeObjects(at: set as IndexSet)
}
print(listArray.count)

log prints: 111 24 87 but the problem is that the listArray contains the same object in of all its indexes. Before removing the objects all objects are different as intended.

ListArray is an array of dictionaries where dictionary has 4 keys:

{
    Date = Date();
    Source = String;
    Title = String;
    Url = String;
}

whereas listToBeRemoved is an array of IndexPaths e.g.:

(
"<NSIndexPath: 0xf7e2dd0ccbb6f985> {length = 2, path = 0 - 63}",
"<NSIndexPath: 0xf7e2dd0cc916f985> {length = 2, path = 0 - 42}",
"<NSIndexPath: 0xf7e2dd0cc936f985> {length = 2, path = 0 - 43}",
"<NSIndexPath: 0xf7e2dd0cc9b6f985> {length = 2, path = 0 - 47}",
"<NSIndexPath: 0xf7e2dd0cca56f985> {length = 2, path = 0 - 48}"

)

Any advice? Thanks in advance

Can you show what listArray and listToBeRemoved are? It would make debugging easier — aheze
– aheze, Commented Nov 18, 2020 at 20:11
let indices = listToBeRemoved.map{ $0.row }.sorted(); indices.reversed().forEach{ listArray.remove(at: $0) } ? — Larme
– Larme, Commented Nov 18, 2020 at 20:20
@Larme Already tried that before... seems to break my dictionaries and still produces multiple same objects — snksnk
– snksnk, Commented Nov 18, 2020 at 20:28
It shouldn't break anything. But does listToBeRemoved contains duplicates values. If so, that needs to be fixed with let indices = Array(Set(listToBeRemoved.map{ $0.row })).sorted(). — Larme
– Larme, Commented Nov 18, 2020 at 20:30

koen · Accepted Answer · 2023-10-14 12:43:10Z

1

What you can do:

Get all indices
Sort them descending
Iterate over the indices, and remove the item at that index

Why reversed? Because else, imagine you have the indices [0, 1], and your array is [A, B, C] If you start looping on the indices, you'll have : 0: Remove first from [A, B, C] -> [B, C] 1: Remove second from [B, C] -> [B]

So, if you are using Swift Array:

let indices = listToBeRemoved.map{ $0.row }.sorted()
indices.reversed().forEach{ listArray.remove(at: $0) }

Since you are using NSMutableArray (I'd strongly recommend you to avoir NSStuff when Stuff is available): listArray.remove(at: $0) is listArray.removeObject(at: $0)

Another possible solution:

let indices = IndexSet(listToBeRemoved.map{ $0.row })
listArray.removeObjects(at: indices) //Objective-C
listArray.remove(atOffsets: indices) //Swift

edited Oct 14, 2023 at 12:43

koen

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answered Nov 19, 2020 at 18:18

Larme

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