{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 模拟场景渲染过程中驱动actor和绘图actor的信息交互过程"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "本例将表示几何图形的一组类的实例发送给actor，该actor将这组实例绘制到显示屏上。像是渲染工厂（rendering farm）在为动画生成场景。一旦场景渲染完毕，构成的场景的几何图形便会被发送给某一actor进行展示。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defined \u001b[32mclass \u001b[36mPoint\u001b[0m\n",
       "defined \u001b[32mclass \u001b[36mShape\u001b[0m\n",
       "defined \u001b[32mclass \u001b[36mCircle\u001b[0m\n",
       "defined \u001b[32mclass \u001b[36mRectangle\u001b[0m\n",
       "defined \u001b[32mclass \u001b[36mTriangle\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "case class Point(x: Double = 0.0, y: Double = 0.0)\n",
    "\n",
    "abstract class Shape() {\n",
    "    // draw方法接受一个函数参数\n",
    "    // 每个图形对象都会将自己的字符格式传给函数f，由f完成绘制工作\n",
    "    def draw(f: String => Unit): Unit = f(s\"draw: ${this.toString}\")\n",
    "}\n",
    "\n",
    "case class Circle(center: Point, radius: Double) extends Shape\n",
    "case class Rectangle(lowerLeft: Point, height: Double, width: Double) extends Shape\n",
    "case class Triangle(point1: Point, point2: Point, point3: Point) extends Shape"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "样本类（case class）让编译器自动生成很多方法，比如String、equals和hashCode方法。编译器还会为样本类同时生成一个伴生对象。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\u001b[36mp20\u001b[0m: \u001b[32mPoint\u001b[0m = \u001b[33mPoint\u001b[0m(\u001b[32m2.0\u001b[0m, \u001b[32m0.0\u001b[0m)\n",
       "\u001b[36mp20b\u001b[0m: \u001b[32mPoint\u001b[0m = \u001b[33mPoint\u001b[0m(\u001b[32m2.0\u001b[0m, \u001b[32m0.0\u001b[0m)\n",
       "\u001b[36mp02\u001b[0m: \u001b[32mPoint\u001b[0m = \u001b[33mPoint\u001b[0m(\u001b[32m0.0\u001b[0m, \u001b[32m2.0\u001b[0m)"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "// Scala调用生成的equals方法来判断==这样的逻辑比较\n",
    "val p20 = new Point(2.0)\n",
    "val p20b = new Point(2.0)\n",
    "val p02 = new Point(y = 2.0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\u001b[36mres2\u001b[0m: \u001b[32mBoolean\u001b[0m = false"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "p20 == p02"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\u001b[36mres3\u001b[0m: \u001b[32mBoolean\u001b[0m = true"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "p20 == p20b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\u001b[36mp1\u001b[0m: \u001b[32mPoint\u001b[0m = \u001b[33mPoint\u001b[0m(\u001b[32m1.0\u001b[0m, \u001b[32m2.0\u001b[0m)"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "// 使用Point伴生类的apply方法\n",
    "\n",
    "val p1 = Point.apply(1.0, 2.0)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Point.apply是构造Point对象的工厂方法，调用该方法就好像不通过new关键字调用Point的构造器一样。\n",
    "``` scala\n",
    "object Point {\n",
    "  def apply(x: Double = 0.0, y: Double = 0.0) = new Point(x, y)\n",
    "  ...\n",
    "}\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "以上定义好了形状类型，接下来回到actor上"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defined \u001b[32mobject \u001b[36mMessages\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "object Messages {\n",
    "    object Exit\n",
    "    object Finished\n",
    "    case class Response(message: String)\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": []
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "load.jar(\"D:\\\\scala\\\\lib\\\\akka-actor_2.11-2.3.10.jar\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\u001b[32mimport \u001b[36makka.actor.Actor\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "import akka.actor.Actor"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "此处定义了一个actor类，用于绘制图形。实现了抽象方法Actor.receive，该方法是Actor的子类必须实现的方法，定义了如何处理接收到的消息。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defined \u001b[32mclass \u001b[36mShapesDrawingActor\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "class ShapesDrawingActor extends Actor {\n",
    "    import Messages._\n",
    "    \n",
    "    def receive = {\n",
    "        case s: Shape =>\n",
    "            s.draw(str => println(s\"ShapesDrawingActor: $str\"))\n",
    "            sender ! Response(s\"ShapesDrawingActor: $s drawn\")\n",
    "        case Exit =>\n",
    "            println(s\"ShapesDrawingActor: exiting...\")\n",
    "            sender ! Finished\n",
    "        case unexpected => //default. Equivalent to \"unexpected: Any\"\n",
    "            val response = Response(s\"Error: Unknown message: $unexpected\")\n",
    "            println(s\"ShapesDrawingActor: $response\")\n",
    "            sender ! response\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "receive是偏函数，接受单一的Any类型参数并返回Unit值。由于该函数返回Unit对象，因此函数体一定会产生副作用。由于actor系统采用了异步消息机制，它必须依靠副作用。通常由于传递消息后无法返回任何消息，代码块中便会发送一些其他消息，包括给发送者的返回消息。\n",
    "\n",
    "偏函数中仅包含了一些case子句，对传递给函数的消息执行模型匹配。receive方法会尝试将接受到的各条消息与编写的模式匹配表达式进行匹配，并执行最先被匹配上的表达式。\n",
    "\n",
    "Actor.sender函数返回了actor发送消息接收方的对象引用，而！方法用于发送异步消息。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "\u001b[32mimport \u001b[36makka.actor.{Props, ActorRef, ActorSystem}\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "import akka.actor.{Props, ActorRef, ActorSystem}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defined \u001b[32mobject \u001b[36mStart\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "object Start"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defined \u001b[32mclass \u001b[36mShapesDrawingDriver\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "class ShapesDrawingDriver(drawerActor: ActorRef) extends Actor {\n",
    "    import Messages._\n",
    "    \n",
    "    def receive = {\n",
    "        case Start =>\n",
    "            drawerActor ! Circle(Point(0.0, 0.0), 1.0)\n",
    "            drawerActor ! Rectangle(Point(0.0, 0.0), 2, 5)\n",
    "            drawerActor ! 3.14159\n",
    "            drawerActor ! Triangle(Point(0.0, 0.0), Point(2.0, 0.0), Point(1.0, 2.0))\n",
    "            drawerActor ! Exit\n",
    "        case Finished =>\n",
    "            println(s\"ShapesDrawingDriver: cleaning up...\")\n",
    "            context.system.shutdown()\n",
    "        case response: Response =>\n",
    "            println(\"ShapesDrawingDriver: Response =\" + response)\n",
    "        case unexpected =>\n",
    "            println(\"ShapesDrawingDriver: ERROR: Receive an unexpected message =\" + unexpected)\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "接下来是驱动应用的主方法，首先构建一个akka.actor.ActorSystem对象和两个actor对象，然后将ShapesDrawingActor对象的引用传递给ShapesDrawingDriver，最后向驱动对象发送Start命令，启动应用。"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "defined \u001b[32mobject \u001b[36mShapesDrawingApp\u001b[0m"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "object ShapesDrawingApp extends App{\n",
    "    val system = ActorSystem(\"DrawingActorSystem\")\n",
    "    val drawer = system.actorOf(Props(new ShapesDrawingActor), \"drawingActor\")\n",
    "    val driver = system.actorOf(Props(new ShapesDrawingDriver(drawer)), \"drawingService\")\n",
    "    driver ! Start\n",
    "    system.shutdown\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "最后结果如图：\n",
    "![](images/shapes_result.jpg)"
   ]
  }
 ],
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