Filter array by indices

ios, swift

Solution

`IndexSet` is a collection of increasing integers, therefore you can map each index to the corresponding array element:

let array = ["sun", "moon", "star", "meteor"]
let indexSet: IndexSet = [2, 3]

let result = indexSet.map { array[$0] } // Magic happening here!
print(result) // ["star", "meteor"]

This assumes that all indices are valid for the given array. If that is not guaranteed then you can filter the indices (as @dfri correctly remarked):

let result = indexSet.filteredIndexSet { $0 < array.count }.map { array[$0] }

Problem

I have an array of elements. I also have an IndexSet that specifies which indices of the array need to be extracted into a new array. E.g.: ``` let array = ["sun", "moon", "star", "meteor"] let indexSet: IndexSet = [2, 3] // Some magic happens here to get: let result = ["star", "meteor"] ``` I'm looking to use the swift `filter` function, but haven't got the answer yet. How can I do this?

Original source