Clean way to filter an array of dictionaries by unique dictionary values

Question

Say I have an object:

struct Foo {
    let id: Int
    let bar: Int
}

Now I have 5 of these objects in an array:

let foo1 =         


        

Answer 1

I'm not a fan of the accepted answer. Having the set outside the closure that uses it doesn't seem appropriate. I would rather keep everything contained. There's a CS term that applies but I don't remember what it is...

I would rather see this:

let uniquedBars = fooArray
    .reduce(into: (result: [Foo](), set: Set())) { partial, next in
        if partial.set.insert(next.bar).inserted {
            partial.result.append(next)
        }
    }
    .result