Map array of objects to Dictionary in Swift

Question

I have an array of Person\'s objects:

class Person {
   let name:String
   let position:Int
}

and the array is:

Answer 1

This is what I have been using

struct Person {
    let name:String
    let position:Int
}
let persons = [Person(name: "Franz", position: 1),
               Person(name: "Heinz", position: 2),
               Person(name: "Hans", position: 3)]

var peopleByPosition = [Int: Person]()
persons.forEach{peopleByPosition[$0.position] = $0}

Would be nice if there was a way to combine the last 2 lines so that peopleByPosition could be a let.

We could make an extension to Array that does that!

extension Array {
    func mapToDict(by block: (Element) -> T ) -> [T: Element] where T: Hashable {
        var map = [T: Element]()
        self.forEach{ map[block($0)] = $0 }
        return map
    }
}

Then we can just do

let peopleByPosition = persons.mapToDict(by: {$0.position})