Swift Arrays: Slices

Swift Arrays: Slices

Use ranges to create slices of arrays.

A range is a half-open interval, meaning it includes the lower bound but excludes the upper bound.

A slice is a view of an array that shares storage with the base array, meaning it is a reference to a portion of the array.

When you modify a slice, the base array is also modified.

ArraySlice

Create an ArraySlice with a range on an array.

Convert to Array if you need its own storage.

let nums = [10, 20, 30, 40, 50]
let middle = nums[1...3]          // ArraySlice<Int>
print(middle)                     // [20, 30, 40]
let copy = Array(middle)          // Array<Int>
print(copy)

Use a half-open range to exclude the upper bound:

let nums = [10, 20, 30, 40, 50]
let slice = nums[1..<3]   // indices 1 and 2
print(slice)               // [20, 30]

Slices share storage with the base array until you copy.

One-Sided Slices

Use one-sided ranges to slice from the start or to the end.

let arr = [0, 1, 2, 3, 4]
print(arr[...2])  // first three elements (0...2)
print(arr[2...])  // from index 2 to the end