[Get unique items in an array based on hash] #Swift

arrayunique.swift

extension Sequence where Iterator.Element: Hashable {
    func unique() -> [Iterator.Element] {
        // Usage
        // print(array.unique()) // prints: [1, 2, 3]
        var seen: Set<Iterator.Element> = []
        return filter { seen.insert($0).inserted }
    }
}