How to remove an element from an array in Swift

Solution 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" }

Solution 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

Solution 3:

The above answers seem to presume that you know the index of the element that you want to delete.

Often you know the reference to the object you want to delete in the array. (You iterated through your array and have found it, e.g.) In such cases it might be easier to work directly with the object reference without also having to pass its index everywhere. Hence, I suggest this solution. It uses the identity operator !==, which you use to test whether two object references both refer to the same object instance.

func delete(element: String) {
    list = list.filter { $0 !== element }
}

Of course this doesn't just work for Strings.

Solution 4:

Swift 5: Here is a cool and easy extension to remove elements in an array, without filtering :

   extension Array where Element: Equatable {

    // Remove first collection element that is equal to the given `object`:
    mutating func remove(object: Element) {
        guard let index = firstIndex(of: object) else {return}
        remove(at: index)
    }

}

Usage :

var myArray = ["cat", "barbecue", "pancake", "frog"]
let objectToRemove = "cat"

myArray.remove(object: objectToRemove) // ["barbecue", "pancake", "frog"]

Also works with other types, such as Int since Element is a generic type:

var myArray = [4, 8, 17, 6, 2]
let objectToRemove = 17

myArray.remove(object: objectToRemove) // [4, 8, 6, 2]