Sequence+SortUsingKeyPath.swift

extension Sequence {
    func sorted<T: Comparable>(by keyPath: KeyPath<Element, T>, comparator: (T, T) -> Bool = { $0 < $1 }) -> [Element] {
        return sorted(by: { (e1, e2) -> Bool in
            return comparator(e1[keyPath: keyPath], e2[keyPath: keyPath])
        })
    }
}

let names = ["Alice", "Bob", "Charlie", "Dave"]
assert(names.sorted(by: \.count) == ["Bob", "Dave", "Alice", "Charlie"])