Find out length of linked list in swift

Swift program for Find out length of linked list. Here problem description and explanation.

import Foundation
// Swift 4 Program for
// Find the length of linked list 

// Linked list node
class LinkNode
{
	var data: Int;
	var next: LinkNode? ;
	init(_ value: Int)
	{
		self.data = value;
		self.next = nil;
	}
}
class SingleLL
{
	var head: LinkNode? ;
	var tail: LinkNode? ;
	init()
	{
		self.head = nil;
		self.tail = nil;
	}
	// Insert new node at the last
	func insert(_ value: Int)
	{
		// Create new node
		let node: LinkNode? = LinkNode(value);
		if (self.head == nil)
		{
			self.head = node;
		}
		else
		{
			// Add new node at the end
			self.tail!.next = node;
		}
		self.tail = node;
	}
	// Count number of nodes and 
	// returns the number of nodes
	func findLength() -> Int
	{
		var temp: LinkNode? = self.head;
		var count: Int = 0;
		while (temp  != nil)
		{
			// Visit to next node
			temp = temp!.next;
			// Increase the node counter
			count += 1;
		}
		return count;
	}
	// Display all Linked List elements
	func display()
	{
		if (self.head  != nil)
		{
			print("Linked List Element", terminator: " : ");
			var temp: LinkNode? = self.head;
			while (temp  != nil)
			{
				print(temp!.data, terminator: "  ");
				temp = temp!.next;
			}
		}
		else
		{
			print("Empty Linked list");
		}
	}
	static func main(_ args: [String])
	{
		let task: SingleLL? = SingleLL();
		task!.insert(5);
		task!.insert(10);
		task!.insert(15);
		task!.insert(20);
		task!.insert(25);
		task!.insert(30);
		task!.insert(35);
		task!.display();
		print("\nLength :",task!.findLength());
	}
}
SingleLL.main([String]());

Output

Linked List Element : 5  10  15  20  25  30  35
Length : 7