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Remove all instances of an object from an array

Swift version: 5.2

Paul Hudson    @twostraws   

Arrays already have methods to find and remove a single item, or remove all items at once, but for removing all instances of a specific item you need to use a closure-based method called removeAll(where:).

For example, given these numbers:

var numbers = [2, 1, 2, 3, 2, 4, 2, 5]

If we wanted to remove all instances of 2 from that array, we could use removeAll(where:) like this:

numbers.removeAll { $0 == 2 }

If you want to return the array with items removed rather than doing it in place, you’d need to write your own extension to Array, like this:

extension Array where Element: Equatable {
    func removing(_ obj: Element) -> [Element] {
        return filter { $0 != obj }
    }
}

Now you can write let removed = numbers.removing(2) to get back [1, 3, 4, 5].

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