Linked List

node.swift

class NodeImpl {
    var node: Node?
    
    func copy() -> NodeImpl {
        let copy = NodeImpl()
        copy.node = node
        return copy
    }
}

struct Node: CustomStringConvertible {
    var impl = NodeImpl()
    
    var value: Int
    var next: Node? {
        get {
            return impl.node
        }
        
        set {
            if !isUniquelyReferencedNonObjC(&impl) {
                impl = impl.copy()
            }
            impl.node = newValue
        }
    }
    
    init(_ value: Int, next: Node?) {
        self.value = value
        self.next = next
    }
    
    var description: String {
        if let next = next {
            return "\(value) -> \(next)"
        }
        else {
            return "\(value) -> X"
        }
    }
}

let n = Node(2, next: nil)
print(n)

let m = Node(6, next: n)
print(m)

var z = m
z.value = 8
z.next = m

print(z)
print(m)