swift, useful example of keypath

extension Sequence {

    func sorted<T: Comparable>(by keyPath:KeyPath<Element, T>) -> [Element]{

        return sorted {a, b in

            return a[keyPath: keyPath] < b[keyPath:keyPath]

        }

    }

    

    func map <T> (_ keyPath: KeyPath<Element, T>) -> [T] {

        return map {$0[keyPath: keyPath]}

    }

    

    func min <T: Comparable> (_ keyPath: KeyPath<Element, T>) -> T? {

        return map(keyPath).min()

    }

    

    func max<T: Comparable> (_ keyPath: KeyPath<Element, T>) -> T? {

        return map(keyPath).max()

    }

    

}