Code:
let oldNums: [Int] = [1, 2, 3, 4, 5 ,6 , 7, 8, 9, 10]
var newArray = oldNums[1..<4]
newArray.insert(99, atIndex: 0) // <-- crash here
newArray.insert(99, atIndex: 1) // <-- work very well
I thank the newArray is a new mutable variable. So I get confuse.
Why? I can't insert a new element into "newArray"
A small code will clarify some points:
let oldNums: [Int] = [1, 2, 3, 4, 5 ,6 , 7, 8, 9, 10]
var newArray = oldNums[1..<4]
print(newArray.dynamicType) //->ArraySlice<Int>
print(newArray.indices) //->1..<4The `newArray` is not an Array and its `indices` is not 0..<3 .
Starting from version "I don't remember", swift slices maintain the original array indexes and the last reason to use they just vanished.
newArray = oldNums[a..<b] will contains elements from a to b-1 (inclusive), and not from 0 to b-a-1 (inclusive).
I know: it's crazy.
P.S. Sorry for my bad english.
A small code will clarify some points:
let oldNums: [Int] = [1, 2, 3, 4, 5 ,6 , 7, 8, 9, 10]
var newArray = oldNums[1..<4]
print(newArray.dynamicType) //->ArraySlice<Int>
print(newArray.indices) //->1..<4The `newArray` is not an Array and its `indices` is not 0..<3 .
Thanks in advance
finally, I got it, It's not real an Array. It's an ArraySlice and It's not zero-based.
So, To insert an element at the beginning of the slice, I can use
newArray.insert(99, atIndex: newArray.startIndex)I think this could help you .
var newArray = Array(oldNums[1..<4])