How to remove an element from an array in Swift

Question

How can I unset/remove an element from an array in Apple's new language Swift?

Here's some code:

let animals = ["cats", "dogs", "chimps", "moose"]

How could the element animals[2] be removed from the array?

Answer 1

The let keyword is for declaring constants that can't be changed. If you want to modify a variable you should use var instead, e.g:

var animals = ["cats", "dogs", "chimps", "moose"]

animals.remove(at: 2)  //["cats", "dogs", "moose"]

A non-mutating alternative that will keep the original collection unchanged is to use filter to create a new collection without the elements you want removed, e.g:

let pets = animals.filter { $0 != "chimps" }

Answer 2

Given

var animals = ["cats", "dogs", "chimps", "moose"]

Remove first element

animals.removeFirst() // "cats"
print(animals)        // ["dogs", "chimps", "moose"]

Remove last element

animals.removeLast() // "moose"
print(animals)       // ["cats", "dogs", "chimps"]

Remove element at index

animals.remove(at: 2) // "chimps"
print(animals)           // ["cats", "dogs", "moose"]

Remove element of unknown index

For only one element

if let index = animals.firstIndex(of: "chimps") {
    animals.remove(at: index)
}
print(animals) // ["cats", "dogs", "moose"]

For multiple elements

var animals = ["cats", "dogs", "chimps", "moose", "chimps"]

animals = animals.filter(){$0 != "chimps"}
print(animals) // ["cats", "dogs", "moose"]

Notes

• The above methods modify the array in place (except for filter) and return the element that was removed.
• Swift Guide to Map Filter Reduce
• If you don't want to modify the original array, you can use dropFirst or dropLast to create a new array.

Updated to Swift 5.2