private

class Counter {
    let inc: () -> Int
    let dec: () -> Int

    init(start: Int) {
        var n = start

        inc = { ++n }
        dec = { --n }
    }
}


let c = Counter(start: 10)

c.inc()  // 11
c.inc()  // 12
c.dec()  // 11

By our discussion on friday, you can even do:

init(var start: Int) {
    inc = { ++start }
    dec = { --start }
}

@Ciechan ✨