How to extend Array to dedup elements using Set?

Question

I have this function that dedups arrays by returning an array of its set.

func dedup<T: Hashable>(_ a: [T]) -> [T] {
    return Array(Set(a))
}

let dirty = ["apple", "apple", "kiwi", "mango"]
let clean = dedup(dirty)

print(clean)

However, I can't figure out how to make this an extension of Array.

extension Array where Element: Hashable {

    static func deduped() -> Array {
        return Array(Set<Element>(self))
    }

}

The error I get is that self does not conform to expected type Sequence.

But note this is a poor algorithm as your array will be both deduped and shuffled. — matt, Nov 17 '19 at 20:18

vadian · Accepted Answer · 2019-11-17T20:27:20.007

2

deduped() must be an instance method, and – more descriptive and not related to the issue – return [Element] rather than Array

extension Array where Element: Hashable {

    func deduped() -> [Element] {
        return Array(Set(self))
    }
}

However here are more efficient ways to remove duplicates, my favorite is

extension Array where Element: Hashable {
    func deduped() -> [Element] {
        var seen = Set<Element>()
        return filter{ seen.insert($0).inserted }
    }
}

edited Nov 17 '19 at 20:27

answered Nov 17 '19 at 20:14

vadian

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I’m pretty sure you don’t have to say `Set`, just Set should be enough. – matt Nov 17 '19 at 20:17
That's a pretty good favorite, I'm going to use it. But the shuffling of the order aside, the original function is as efficient as it gets, no? – lurning too koad Nov 17 '19 at 20:29
Run tests of both algorithms and measure the execution time. – vadian Nov 17 '19 at 20:46

How to extend Array to dedup elements using Set?

1 Answers1