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    "<p style=\"float: left;\"><a href=\"packages-and-imports.ipynb\" target=\"_blank\">Previous</a></p>\n",
    "<p style=\"text-align:center;\">Tour of Scala</p>\n",
    "<div style=\"clear: both;\"></div>\n",
    "\n",
    "# Package Objects\n",
    "\n",
    "# Package objects\n",
    "\n",
    "Scala provides package objects as a convenient container shared across an entire package.\n",
    "\n",
    "Package objects\n",
    "can contain arbitrary definitions, not just variable and method definitions. For instance, they are frequently\n",
    "used to hold package-wide type aliases and implicit conversions. Package objects can even inherit\n",
    "Scala classes and traits.\n",
    "\n",
    "By convention, the source code for a package object is usually put in a source file named `package.scala`.\n",
    "\n",
    "Each package is allowed to have one package object. Any definitions placed in a package object are considered\n",
    "members of the package itself.\n",
    "\n",
    "See example below. Assume first a class `Fruit` and three `Fruit` objects in a package\n",
    "`gardening.fruits`:"
   ]
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  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "```\n",
    "// in file gardening/fruits/Fruit.scala\n",
    "package gardening.fruits\n",
    "\n",
    "case class Fruit(name: String, color: String)\n",
    "object Apple extends Fruit(\"Apple\", \"green\")\n",
    "object Plum extends Fruit(\"Plum\", \"blue\")\n",
    "object Banana extends Fruit(\"Banana\", \"yellow\")\n",
    "```\n"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Now assume you want to place a variable `planted` and a method `showFruit` directly into package `gardening`.\n",
    "Here's how this is done:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "```\n",
    "// in file gardening/fruits/package.scala\n",
    "package gardening\n",
    "package object fruits {\n",
    "  val planted = List(Apple, Plum, Banana)\n",
    "  def showFruit(fruit: Fruit): Unit = {\n",
    "    println(s\"${fruit.name}s are ${fruit.color}\")\n",
    "  }\n",
    "}\n",
    "```\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "As an example of how the use site looks, the following object `PrintPlanted` imports `planted` and `showFruit` in exactly the same\n",
    "way it imports class `Fruit`, using a wildcard import on package gardening.fruits:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "```\n",
    "// in file PrintPlanted.scala\n",
    "import gardening.fruits._\n",
    "object PrintPlanted {\n",
    "  def main(args: Array[String]): Unit = {\n",
    "    for (fruit <- fruits.planted) {\n",
    "      showFruit(fruit)\n",
    "    }\n",
    "  }\n",
    "}\n",
    "```\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Package objects are like other objects, which means you can use inheritance for building them. For example, one might mix in a couple of traits:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "```\n",
    "package object fruits extends FruitAliases with FruitHelpers {\n",
    "  // helpers and variables follows here\n",
    "}\n",
    "```\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Note that method overloading doesn't work in package objects.\n",
    "<p style=\"float: left;\"><a href=\"packages-and-imports.ipynb\" target=\"_blank\">Previous</a></p>\n",
    "<p style=\"text-align:center;\">Tour of Scala</p>\n",
    "<div style=\"clear: both;\"></div>"
   ]
  }
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