How can pivoting an array in swift

Question

With this code I create the array

struct Item {
    let expense  : String
    let year     : String
    let value   : Float
}
var resultArray = [Item]()
resultArray.append(Item(expense: "Restaurant", year: "2019", value: 1000))
resultArray.append(Item(expense: "Restaurant", year: "2020", value: 500))
resultArray.append(Item(expense: "Restaurant", year: "2021", value: 100))
resultArray.append(Item(expense: "Gym",        year: "2019", value: 100))
resultArray.append(Item(expense: "Gym",        year: "2020", value: 100))
resultArray.append(Item(expense: "Gas",        year: "2020", value: 200))
resultArray.append(Item(expense: "Gas",        year: "2021", value: 50))

If I were to represent the result in the form of an excel table, I would get this

I would like obtain this, but I don't know how:

Thank you

Answer 1

等待大神答复