Swift: Removing Elements from a Set (4 Examples)

Updated: May 10, 2023 By: Khue Post a comment

This concise, practical article will walk you through several unique examples that demonstrate how to remove single or multiple elements from a set in Swift. Without any further ado (like explaining what Swift is or talking about the history of the language), let’s get started.

Table Of Contents

1 Using the remove() method

2 Removing a random element from a set

3 Removing all elements from a set

4 Removing elements from a set based on a condition

Using the remove() method

In cases where you want to remove a specific element from a set based on its value, the remove() method is the best choice. This method takes the element you want to remove as a parameter and returns it if it was a member of the set; otherwise, it returns nil.

Example:

var mySet:Set<String> = ["Sling Academy", "Swift", "iOS"]

// remove "iOS" from the set
let removedElement: String? = mySet.remove("iOS")

// print the set after removing "iOS"
print(mySet)

Output:

["Sling Academy", "Swift"]

Removing a random element from a set

If you want to remove a random element from a set, just simply use the removeFirst() method. Don’t let the name of the method confuse you (“removeFirst” doesn’t really mean “remove the first element”). A set in Swift is an unordered collection, so who can tell which is its first element?

Example:

var numbers = Set([1, 2, 3, 4, 5, 6, 7])

let firstNumber = numbers.removeFirst()

print("The removed number is \(firstNumber).")
print("The remaining numbers are \(numbers).")

Output:

The removed number is 4.
The remaining numbers are [3, 6, 7, 2, 1, 5].

Note that the output isn’t consistent due to the randomness.

Removing all elements from a set

The removeAll() method can clear a set and leaves it empty.

var strings:Set<String> = ["a", "b", "c"]
strings.removeAll()
print("The set after removing all items: \(strings)")

Output:

The set after removing all items: []

Removing elements from a set based on a condition

In order to remove elements that satisfy a condition from a set, you can use the filter() method.

Example:

var numbers: Set<Int> = [2, 3, 5, 7, 9, 11, 6, 10]

// get a new set with only even numbers
let evenNumbers: Set<Int> = numbers.filter { $0 % 2 == 0 }

// print
print(evenNumbers)

Output:

[10, 6, 2]

An alternative solution is to convert the set to an array, then call the removeAll(where:) method on that array:

var numbers: Set<Int> = [2, 3, 5, 7, 9, 11, 6, 10]

var array = Array(numbers)

// remove all odd numbers from array
array.removeAll(where: { $0 % 2 != 0 })

// convert the array back to a set
numbers = Set(array)

// print the final result
print(numbers)

Output: