Adjacency list representation of undirected graph in swift

Swift program for Adjacency list representation of undirected graph. Here problem description and explanation.

import Foundation
/*
    Swift 4 Program for 
    Undirected graph representation by using adjacency list 
*/
class AjlistNode
{
	// Vertices node key
	var id: Int;
	var next: AjlistNode? ;
	init(_ id: Int)
	{
		// Set value of node key
		self.id = id;
		self.next = nil;
	}
}
class Vertices
{
	var data: Int;
	var next: AjlistNode? ;
	var last: AjlistNode? ;
	init(_ data: Int)
	{
		self.data = data;
		self.next = nil;
		self.last = nil;
	}
}
class Graph
{
	// Number of Vertices
	var size: Int;
	var node: [Vertices? ];
	init(_ size: Int)
	{
		// Set value
		self.size = size;
		self.node = Array(repeating: nil, count: size);
		self.setData();
	}
	// Set initial node value
	func setData()
	{
		if (self.size <= 0)
		{
			print("\nEmpty Graph");
		}
		else
		{
			var index: Int = 0;
			while (index < self.size)
			{
				self.node[index] = Vertices(index);
				index += 1;
			}
		}
	}
	// Connect two nodes
	func connect(_ start: Int, _ last: Int)
	{
		let edge: AjlistNode? = AjlistNode(last);
		if (self.node[start]!.next == nil)
		{
			self.node[start]!.next = edge;
		}
		else
		{
			// Add edge at the end
			self.node[start]!.last!.next = edge;
		}
		// Get last edge 
		self.node[start]!.last = edge;
	}
	//  Handling the request of adding new edge
	func addEdge(_ start: Int, _ last: Int)
	{
		if (start >= 0 && start < self.size && 
            last >= 0 && last < self.size)
		{
			self.connect(start, last);
			if (start == last)
			{
				// When self loop
				return;
			}
			self.connect(last, start);
		}
		else
		{
			// When invalid nodes
			print("\nHere Something Wrong");
		}
	}
	func printGraph()
	{
		if (self.size > 0)
		{
			do {
				var index: Int = 0;
				// Print graph ajlist Node value
				while (index < self.size)
				{
					print("\nAdjacency list of vertex " + String(index), 
                          terminator: " :");
					var temp: AjlistNode? = self.node[index]!.next;
					while (temp  != nil)
					{
						// Display graph node 
						print("  " + String(self.node[temp!.id]!.data), 
                              terminator: "");
						// Visit to next edge
						temp = temp!.next;
					}
					index += 1;
				}
			}
		}
	}
	static func main(_ args: [String])
	{
		// 5 implies the number of nodes in graph
		let g: Graph? = Graph(5);
		// Connect node with an edge
		g!.addEdge(0, 1);
		g!.addEdge(0, 2);
		g!.addEdge(0, 4);
		g!.addEdge(1, 2);
		g!.addEdge(1, 4);
		g!.addEdge(2, 3);
		g!.addEdge(3, 4);
		// print graph element
		g!.printGraph();
	}
}
Graph.main([String]());

Output

Adjacency list of vertex 0 :  1  2  4
Adjacency list of vertex 1 :  0  2  4
Adjacency list of vertex 2 :  0  1  3
Adjacency list of vertex 3 :  2  4
Adjacency list of vertex 4 :  0  1  3