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We've talked about a raise in Swift, which is a collection of similar objects.



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Now there's a special sub array, if you like, called a set in Swift and you get it in a few other



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languages, but not that many, as I recall.



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This is called a set because it is literally a set of items.



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Again, they're all the same kind of item.



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But if you think about what a set is in real life, a set is a collection of things that doesn't have



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a repeat.



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So if I have a set of baseball cards, then that set has one of each baseball player of whatever team



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I'm targeting.



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You wouldn't put two of the same player in the set, would you?



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So that's a handy way to remember sets.



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And here's an example we have var faves is a set of strings, which is rock, classical and hip hop,



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which is obviously musical styles.



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What if I want to add a fave into this.



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Well, faves dot, if you remember ARray's we used append with this.



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It's not so straightforward because we use insert now.



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The subtle difference between append and insert is that append add something to the end at the end is



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close enough to add end to remember insert just puts something in to the set of items.



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If that new something is the same as something that's already in the set, there'll be no change to



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the size of it and that same thing will only appear once.



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Right.



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So I'm going to give you an example.



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First of all, of a lowercase rock are.



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So if we play this, that set now has four items.



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If we print it out, we'll be able to see.



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Hip hop, classical rock and lowercase rock.



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OK, so lower case is obviously different to upper case as far as Swift is concerned.



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In some cases that may not be the case in different languages.



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That could be different, too.



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OK.



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What do we want to do?



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Well, we'd like to see if faves contains rock faves that contains.



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Rock, and if we hit play on that, that should give us true because it is actually there.



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That's how we check if a set contains a value.



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Now, if you were doing a stamp collecting app, for example, you would have this would be ideal for



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it because you'd have one of each stamp and you'd query your app and say, do I have this one?



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You go into the set and say, no, we don't have that one, so please go and collect it.



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Now, we can actually mash these things together, but before we do that, I just want to show you.



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What happens if I actually try and insert another?



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Lower case rock, and then again, I print.



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The favs.



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Rock still only appears once that's the lowercase version, because, like I said, if it's already



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in there, it doesn't care.



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It's just going to not insert that new item for you.



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Right.



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Let's have a var called rubbish.



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What is this?



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This is, again, a set of string.



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Equal to hip hop.



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Now, I'm not saying hip hop's rubbish, I just had to do an example for this.



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I like hip hop sometimes, right?



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Depending on which song, of course.



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And of course, I forgot to put my brackets around.



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So now we have a second set, you might have a friend who has a set of stamps and you have a set and



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you want to merge them and see what full sets you can come out with using that merge.



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And of course, it's the same here.



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We can have five dot union.



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Faves, rather, this should be plural.



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Union with rubbish that's hit play and see what that gives us.



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Right, so we've added in hip hop or we haven't, because when we tried to unionise, it already exists.



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So what I'm going to do is remove it from this top one.



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Now, we should get there we go so it doesn't exist in the original anymore, but when we unión them



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together, smash them together, we get it existing, what other things do we have?



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We have favs dot intersection.



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With rubbish, so this is saying if I bring these two together, what are the similar elements?



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And in this case it should be an empty set because nothing is similar.



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But if I put in.



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That hip hop again.



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Now, our intersection should give us hip hop and there we have it as part of that set.



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We can also do favors that subtracting.



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Returns a new set containing the elements of this set that do not occur in the given sequence.



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This is like doing it's like doing the intersection, but bringing back the elements that don't intersect.



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And then we have favs dot symmetric difference.



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I just copy this to save me from.



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Actually writing it, so if we read all these, we should see what happens, it does the same thing,



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the symmetric difference, I'm not quite sure what the symmetric differences.



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Let's have a look.



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Returns the new set with the elements that are either in this set or in the given sequence, but not



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in both.



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OK, interesting, right?



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I've never actually used this.



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I've used that once or twice in my life.



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But since I have actually used.



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Writes my notes over here say you get a homework break, but let's remove that, so I guess there's



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no homework for this section.



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Lucky you and lucky me, because that's one less video to record.