Linked list implementation in Swift using Sequence protocol

linked-list-w-sequence.swift

class Link<T> { 
  let value: T 
  let nextLink: Link<T>? 
  
  init(_ value: T, next: Link<T>?){ 
    self.value = value 
    self.nextLink = next 
  } 
} 

class LinkedLink<T> : Sequence, IteratorProtocol { 
  var currentNode : Link<T>? 
  
  init(head: Link<T>) { 
    currentNode = head 
  } 
  
  func next() -> T? { 
    if let next = currentNode?.nextLink { 
      currentNode = next return next.value 
    } 
    return nil 
  } 
} 

let elementFour = Link(4, next: nil) 
let elementThree = Link(3, next: elementFour) 
let elementTwo = Link(2, next: elementThree) 
let elementOne = Link(1, next: elementTwo) 
let linkedList = LinkedLink(head: elementOne) 

for item in linkedList { 
  print(item) 
} 
// prints 2 
// prints 3 
// prints 4 

linkedList.contains(2) //true