What does $0 and $1 mean in Swift Closures?

Question

let sortedNumbers = numbers.sort { $0 > $1 }
print(sortedNumbers)

Can anyone explain, what $0 and $1 means in swift?

Answer 1

It represents shorthanded arguments sent into a closure, this example breaks it down:

Swift 4:

var add = { (arg1: Int, arg2: Int) -> Int in
    return arg1 + arg2
}
add = { (arg1, arg2) -> Int in
    return arg1 + arg2
}
add = { arg1, arg2 in
    arg1 + arg2
}
add = {
    $0 + $1
}

let result = add(20, 20) // 40