Swift Basics: Array vs. Set

Most iOS developers instinctively reach for an Array when using collections in Swift. I recommend stopping and thinking if a Set would work better. Sets offer better performance as well as a bunch of powerful methods to compare Sets.

This tutorial was created using Xcode 14 and iOS 16.

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Timestamps:
0:00 - Is there better?
0:29 - Array vs. Set
1:33 - Time Complexity
2:20 - Code Examples
2:47 - Intersection
3:48 - Subtract
4:44 - Disjoint
5:22 - Union
6:06 - Symmetric Difference
7:03 - Subset & Superset
7:55 - Insert, Remove, Contains

[HaraldAchitz]

Just so you know, what you say about performance is only valid for lookup. There are many use-cases where an array is the better solution, even if you scan through the whole thing. Keyword, cache locality . And if you order the array, you will have awesome performance also with search, and the other set operation you showed.
I would suggest you change the title of the video (but for the youtube algo, that one might be good, also to raise engagement, so maybe leave it for clicks 😁 )

[jaila]

Hey Sean, nice video!
You mentioned that Arrays in swift have an O(N) lookup complexity.
Arrays actually conform to the RandomAccessCollection protocol, which buys us back the O(1) complexity for a lot of the array's functionality.

[kavinda_dilshan_paramsoodi]

I think you mistakenly union the same sets instead swiftUIDevs + SwiftDevs.

[kavinda_dilshan_paramsoodi]

Never Knew about Sets. I've been using Arrays all this time. Thanks, sean. Valuable video, and I learned something new today.

[foilhat]

And then you convert sets to arrays anyway to store in Core Data.

[ruslangaliev]

Thanks a lot for this video! It’s was very useful!

[slmille]

Since as Swift devs we're probably doing UI, we should generally be using FetchRequests instead of Arrays or Sets to populate UI. FetchRequests get automatic updates when the database changes and has a sort function built in.

[tokero]

Actually reading from an Array (if you have the index) is O(1) which is often the case...

[Patrick]

I love arrays, back from the old days. But sets are awesome!

[wewhalea]

Great video, but what will you say about pagination and order? How can I avoid an array?

[indomitabletr]

Can you make a video about these methods as well ?
lexicographicallyPrecedes

makeIterator
reserveCapacity
underestimatedCount
withUnsafeBufferPointer
partition

Maybe there are some more.

[arthurdeboer]

What if there are two students with the same name?

[ameyajoshi]

Hey Sean, while I agree with you, I use Sets when I wanna store exclusive values like say an Order Number for a Product that is sold, which is unique.

[abhijeetcherungottil]

Can you give real life example not using set, say can we use it in tableview or anything similar

[vikasgupta]

It's really great and helpful video, and I just give one suggestion, pls add subtitle if possible, because, YouTube CC is not accurate and my English not fluent, so it's really hard for me to understand you Said, I hope you are getting my point. Anyway very helpful video ❤ 😍

[DaveJacobseniOS]

Solid info here! Sets have been a rare encounter in all my development days but they are pretty awesome.

[MosabbirSadman]

Hey Sean! Great content as always!
Got to know about the practical use of the set operators.
Excited to use them from now on 😃
Also wanted to let you know that your fingers might have slipped during demonstrating the union example. 😄
But that's completely understandable...
Looking forward to your next video 😃

[JustinWellsDev]

Sean: When you need a collection of something in Swift, you instinctively reach for an array. Don't you?

Me: 👀

[ToddHoff]

Is the performance difference something you've seen in your apps? Since it's all in memory, I wouldn't think it mattered that much.

[xpopcornx]

Set don't work well with SwiftUI though.