gamekitPath.swift

import GameplayKit

let myGraph = GKGraph()

class MyNode: GKGraphNode {
  let name: String
  var travelCost: [GKGraphNode: Float] = [:]

  init(name: String) {
    self.name = name
    super.init()
  }

  required init?(coder aDecoder: NSCoder) {
    self.name = ""
    super.init()
  }

  override func cost(to node: GKGraphNode) -> Float {
    return travelCost[node] ?? 0
  }

  func addConnection(to node: GKGraphNode, bidirectional: Bool = true, weight: Float) {
    self.addConnections(to: [node], bidirectional: bidirectional)
    travelCost[node] = weight
    guard bidirectional else { return }
    (node as? MyNode)?.travelCost[self] = weight
  }
}

func print(_ path: [GKGraphNode]) {
  path.flatMap({ $0 as? MyNode}).forEach { node in
    print(node.name)
  }
}

func printCost(for path: [GKGraphNode]) {
  var total: Float = 0
  for i in 0..<(path.count-1) {
    total += path[i].cost(to: path[i+1])
  }
  print(total)
}

let nodeA = MyNode(name: "A")
let nodeB = MyNode(name: "B")
let nodeC = MyNode(name: "C")
let nodeD = MyNode(name: "D")
myGraph.add([nodeA, nodeB, nodeC, nodeD])
nodeA.addConnection(to: nodeB, weight: 1.1)
nodeB.addConnection(to: nodeC, weight: 0.1)
nodeC.addConnection(to: nodeD, weight: 1.3)
var path = myGraph.findPath(from: nodeA, to: nodeD)
print(path)
printCost(for: path)

let nodeS = MyNode(name: "S")
nodeS.addConnection(to: nodeA, weight: 0)
nodeS.addConnection(to: nodeD, weight: 1.5)
path = myGraph.findPath(from: nodeA, to: nodeD)
print(path)
printCost(for: path)