Slice that Collection: A Swift guide

What are slices, and how are they used?

Steven Curtis
3 min readApr 26, 2020


Slices make your use of collections in Swift more efficient. This gives us an opportunity to write efficient code and really get to grips with Indices. Shall we get started, then?

Difficulty: Beginner | Easy | Normal | Challenging


  • Some knowledge of Collections in Swift


Array: An ordered series of objects which are the same type

Collection: A sequence of elements that can be traversed (as many times as you want) and can be accessed by an indexed subscript

Enumeration: A complete, ordered listing of the items in a collection

Index: This is where files are placed that you want to commit to the git repository. Also known as the staging area.

Indices: The number position given to an Array

Integer: A number that has no fractional part, that is no digits after the decimal point

Offset: In an array or other data structure, the offset is an Integer representing the distance between the beginning of the data structure and the object in question

Set: An unordered collection of values (where all the values are of the same type)

Slice: A slice of a collection that represents a view onto a subsequence of the master collection

Subscript: A shortcut for accessing the members in an array (or any collection or list, depending on the language)


In Swift, collections (as in other languages) are vitally important. ArraySlices provide a view on an array rather than a new array, meaning that both the initial array and the slice share the same indicies.

This is all covered in my article around ArraySlice, but for review here is a quick summary

The Array Summary

If we have an ages array

let ages = [1,5,12,15,2,26,67,36]

we can take the second and third elements of the ages array, and put it into an arrayslice.