{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "# [X-Village] Lesson04-Overview and Encapsulation\n",
    "by 梁祐承"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## 物件導向程式設計 OOP\n",
    "- Object-oriented programming\n",
    "- 以\"物件\"(Object)作為基本單位\n",
    "- \"物件\"(Object)具有函式(method)和資料(data)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 物件導向的精神\n",
    "- 封裝\n",
    "- 繼承\n",
    "- 多型"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 物件導向程式語言？\n",
    "- 支援Class (物件的模板)\n",
    "- Python / Java / C++ / ......"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 非物件導向程式語言？\n",
    "- 以C語言為例，C沒有直接支援Class\n",
    "- 但是你還是可以把C寫得很物件導向\n",
    "- 同理，Python也可以寫得很不OO"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 物件導向是種概念\n",
    "- 語言支援物件導向只是讓你可以方便使用Class\n",
    "- 重點是 \"物件導向設計\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 為何使用物件導向開發\n",
    "- 適合多人協作\n",
    "- 適合大型專案\n",
    "- 可維護性高\n",
    "- 減少不同程式碼互相干擾"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "#### 想像（一）\n",
    "- 現場有3個人拿著同一型號的手機\n",
    "- 但是容量/顏色不同\n",
    "- 剩餘電量也不同"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "- \"手機\"是個\"物件\"\n",
    "- \"顏色/容量/電量\"是這個物件的\"資料\"\n",
    "- \"手機型號\"是Class\n",
    "- \"Class\" 可以生成多個 \"物件\""
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### Practice 1 (15min)\n",
    "請設計一個Class `Car`，具有`Color`和`Speed`兩種data\n",
    "並用這個Class生成兩個`Car`物件，具有不同的`Color`且預設`Speed`為0"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "#### 想像（二）\n",
    "- 你走進一間空教室準備上課\n",
    "- 教室設備都沒有啟動\n",
    "- 你該做什麼"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "1. 把電燈打開\n",
    "2. 把冷氣打開\n",
    "3. 把投影機打開\n",
    "4. ......"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 回憶\n",
    "- 電腦Bootstrap\n",
    "- BIOS -> Bootloader -> OS -> ..."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "## 但你是怎麼開電腦的？"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "1. 按下開機鍵"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "- \"電腦\"是個\"物件\"\n",
    "- \"開機\"是這個物件的\"函式\"\n",
    "- 函式可以對物件進行操作"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### Practice 2 (15min)\n",
    "修改剛剛的Class `Car`，增加`boost()`和`step_break()`兩個函式，分別讓`speed`增加或減少"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "## 封裝 Encapsulation"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 存取權\n",
    "\n",
    "- 如果一台車不踩煞車直接讓速度變為0會發生什麼事\n",
    "    - 人會飛出去\n",
    "- 所以我們需要保護`speed`不被任意修改"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "ename": "AttributeError",
     "evalue": "'Car' object has no attribute '__speed'",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-20-d64c58a87895>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[1;32m     17\u001b[0m \u001b[0mredCar\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mCar\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'Red'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     18\u001b[0m \u001b[0mredCar\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mboost\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 19\u001b[0;31m \u001b[0mprint\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mredCar\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__speed\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mAttributeError\u001b[0m: 'Car' object has no attribute '__speed'"
     ]
    }
   ],
   "source": [
    "class Car:\n",
    "    color = None\n",
    "    __speed = None\n",
    "    \n",
    "    def __init__(self, color, speed=0):\n",
    "        self.color = color\n",
    "        self.__speed = speed\n",
    "        \n",
    "    def boost(self):\n",
    "        self.__speed += 1\n",
    "        \n",
    "    def step_break(self):\n",
    "        self.__speed -= 1\n",
    "        if self.__speed < 0:\n",
    "            self.__speed = 0\n",
    "            \n",
    "redCar = Car('Red')\n",
    "redCar.boost()\n",
    "print(redCar.__speed)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "## OOPs"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### Getter/Setter\n",
    "- 雖然保護了`speed`, 但還是要讓外界能拿到他的值\n",
    "- 也要保留可以讓外界修改的空間\n",
    "- 保留Getter/Setter可以在外部存取時做控制，不超出設計預期範圍"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### Practice 3 (20min)\n",
    "修改剛剛的Class `Car`\n",
    "1. 增加`get_speed()`函式，回傳Car的`speed`\n",
    "2. 增加`set_speed(newspeed)`函式，若傳入的`newspeed`超過100或小於0就印出錯誤訊息並不要修改`speed`"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### 隱藏實做細節\n",
    "- 你的Class 可能有很多功能，但使用者不需要知道所有細節\n",
    "- 按下開機按鈕就可以開電腦，我不用知道Bootstrap的那一大堆東西！！"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "#### Practice 4 (10min)\n",
    "修改下一頁Code，新增`boot()`函式隱藏開機細節"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Power turned on\n",
      "BIOS loaded\n",
      "Bootloader loaded\n",
      "OS loaded\n",
      "Boot complete\n"
     ]
    }
   ],
   "source": [
    "import time\n",
    "\n",
    "class Computer:\n",
    "    def poweron(self):\n",
    "        pass\n",
    "    def load_BIOS(self):\n",
    "        time.sleep(1)\n",
    "    def load_bootloader(self):\n",
    "        time.sleep(1)\n",
    "    def load_OS(self):\n",
    "        time.sleep(3)\n",
    "        \n",
    "pc = Computer()\n",
    "pc.poweron()\n",
    "print('Power turned on')\n",
    "pc.load_BIOS()\n",
    "print('BIOS loaded')\n",
    "pc.load_bootloader()\n",
    "print('Bootloader loaded')\n",
    "pc.load_OS()\n",
    "print('OS loaded')\n",
    "print('Boot complete')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "source": [
    "#### Class 設計"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "###### 決定所需的 Data\n",
    "- 各class管理自己所需的Data\n",
    "- 若不同的Class有許多相同的data，可以考慮之後提到的繼承\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "###### 決定 Data能見度\n",
    "- 哪些Data完全不該被外部存取\n",
    "- 哪些Data應該透過getter被讀取\n",
    "- 哪些Data可以透過setter被賦值\n",
    "- 哪些Data可以被自由存取"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "###### Data 能見度取捨\n",
    "- 有些人認為所有Data都不該被外部直接存取\n",
    "    - 優點？\n",
    "    - 缺點？\n",
    "- 有些人把所有Data開放給外部存取\n",
    "    - 優點？\n",
    "    - 缺點？"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
     "slide_type": "subslide"
    }
   },
   "source": [
    "###### 決定所需的 Method\n",
    "- 如何控制Data\n",
    "- 如何包裝各種操作\n",
    "- 減少Code重複性\n",
    "- 善用內部 Method"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Practice 5\n",
    "考慮以下小遊戲：\n",
    "```\n",
    "                      ------\n",
    "                      |敵人|\n",
    "   ====================    =====\n",
    "起 玩                            終\n",
    "點 家                            點\n",
    "   =============================\n",
    "   \n",
    "   X軸座標 ---->\n",
    "```\n",
    "\n",
    "請設計玩家和敵人的class\n",
    "- 玩家要可以移動\n",
    "- 玩家具有HP\n",
    "- 玩家具有座標\n",
    "- 敵人有攻擊力\n",
    "- 敵人有攻擊狀態和休息狀態"
   ]
  }
 ],
 "metadata": {
  "celltoolbar": "Slideshow",
  "kernelspec": {
   "display_name": "Python 3",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.6.5"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}