How to turn a String array into an Int array (multidimensional)?

Question

Swift

There is an array

[["9", "6", "7", "8", "5"], ["1", "1", "1", "1", "1"]]

, you need to get a new one
I do and I get an error

let arr = [["9", "6", "7", "8", "5"], ["1", "1", "1", "1", "1"]]
let mapArr = arr.map{Int($0).map{Int($0)}}

although the design itself is working and gives a result

let arr = [[1,2,3],[4,5,6]]
let mapArr = arr.map{$0.map{$0 * 2}}
mapArr // [[2, 4, 6], [8, 10, 12]]

Answer 1

Good afternoon!
In your first example, you are trying to convert an array of strings to Int and you are getting an error.
If you use .map, then it returns an array of optional values. And in this case, if there is a string in the array that cannot be converted to Int, then there will be nil in this place.
If you use flatMap , then it will leave only those values ​​​​that were successfully converted to Int.

let arr = [["9", "6", "7", "8", "5"], ["1", "1", "1", "1", "1"]]
let mapArr = arr.flatMap { $0.flatMap { Int($0) } }