# Swift Sets

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This tutorial belongs to the Swift series

Sets are used to create collections of non-repeated items.

While an array can contain many times the same item, you only have unique items in a set.

You can declare a set of Int values in this way:

``````let set: Set<Int> = [1, 2, 3]
``````

or you can initialize it from an array:

``````let set = Set([1, 2, 3])
``````

Add items to the set using `insert()`:

``````var set = Set([1, 2, 3])
set.insert(17)
``````

Unlike arrays, there is no order or position in a set. Items are retrieved and inserted randomly.

The way to print the content of a set ordered is to transform it into an array using the `sorted()` method:

``````var set = Set([2, 1, 3])
let orderedList = set.sorted()
``````

To check if a set contains an element, use the `contains()` method:

``````var set = Set([1, 2, 3])
set.contains(2) //true
``````

To get the number of items in the set, use the `count` property:

``````let set = Set([1, 2, 3])
set.count //3
``````

If a set is empty, its `isEmpty` property is `true`.

``````let set = Set([1, 2, 3])
set.isEmpty //false
``````

To remove one item from the array, use `remove()` passing the value of the element:

``````var set = Set([1, 2, 3])
set.remove(1)
//set is [2, 3]
``````

To remove all items from the set, you can use removeAll():

``````set.removeAll()
``````

Sets, like arrays, are passed by value, which means if you pass it to a function, or return it from a function, the set is copied.

Sets are great to perform set math operations like intersection, union, subtracting, and more.

These methods help with this:

• `intersection(_:)`
• `symmetricDifference(_:)`
• `union(_:)`
• `subtracting(_:)`
• `isSubset(of:)`
• `isSuperset(of:)`
• `isStrictSubset(of:)`
• `isStrictSuperset(of:)`
• `isDisjoint(with:)`

Sets are collections, and they can be iterated over in loops.

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