idiomatic-kotlin-course/notebooks/Kotlin design patterns.ipynb

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  {
   "cell_type":"markdown",
   "source":[
    "# Sheet"
   ],
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   "metadata":{
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     "type":"MD",
     "hide_input_from_viewers":false,
     "hide_output_from_viewers":false,
     "sheet_delimiter":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Factories"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"kfka3l54zO2cbMlMjZser7",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "interface A{\n",
    "    val body: String\n",
    "}\n",
    "\n",
    "class B(override val body: String): A{\n",
    "    override fun toString() = \"$body B\"\n",
    "}\n",
    "\n",
    "class C(override val body: String): A{\n",
    "    override fun toString() = \"$body C\"\n",
    "}\n",
    "\n",
    "fun print(obj: A){\n",
    "    println(obj)\n",
    "}"
   ],
   "execution_count":9,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"w3yuNLSDBka2TYCaWojtxM",
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   }
  },
  {
   "cell_type":"code",
   "source":[
    "print(C(\"My body\"))"
   ],
   "execution_count":10,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "My body C\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
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  {
   "cell_type":"code",
   "source":[
    "interface AFactory<out T: A>{\n",
    "    fun create(body: String): T\n",
    "}\n",
    "\n",
    "object BFactory: AFactory<B>{\n",
    "    override fun create(body: String): B = B(body)\n",
    "}\n",
    "\n",
    "fun <T: A> createWithAWord(word: String, factory: AFactory<T>) = factory.create(\"Word: $word\")"
   ],
   "execution_count":14,
   "outputs":[],
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   }
  },
  {
   "cell_type":"code",
   "source":[
    "createWithAWord(\"Hello\", BFactory)"
   ],
   "execution_count":15,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "Word: Hello B"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
   "metadata":{
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     "hide_output_from_viewers":true
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  {
   "cell_type":"code",
   "source":[
    "fun <T: A> createWithAWord(word: String, factoryFunction: (String) -> T) = factoryFunction(\"Word: $word\")"
   ],
   "execution_count":17,
   "outputs":[],
   "metadata":{
    "datalore":{
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     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "createWithAWord(\"Hello\", ::B)"
   ],
   "execution_count":19,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "Word: Hello B"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
   "metadata":{
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     "hide_output_from_viewers":true
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  },
  {
   "cell_type":"code",
   "source":[
    "createWithAWord(\"Hello\"){body -> B(\">\\t$body\")}"
   ],
   "execution_count":21,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       ">\tWord: Hello B"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
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     "node_id":"TvX8qzziDGxZWf044iqHO3",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
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  },
  {
   "cell_type":"markdown",
   "source":[
    "# Factory functions"
   ],
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   "cell_type":"code",
   "source":[
    "data class Client(val url: String)\n",
    "\n",
    "interface Request{\n",
    "    val client: Client\n",
    "}\n",
    "\n",
    "data class RequestImpl(override val client: Client): Request{\n",
    "\/\/    constructor(url: String): this(Client(url))\n",
    "}"
   ],
   "execution_count":2,
   "outputs":[],
   "metadata":{
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     "node_id":"yVwMw3CpejJHhnEQDCab6g",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "fun Request(url: String): Request{\n",
    "    return RequestImpl(Client(url))\n",
    "}"
   ],
   "execution_count":4,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"72D1rEcXVM7hutTX65ouiE",
     "type":"CODE",
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     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "Request(\"DDD\")"
   ],
   "execution_count":5,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "RequestImpl(client=Client(url=DDD))"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
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     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "listOf(1,2,3)"
   ],
   "execution_count":33,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "[1, 2, 3]"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"3yvFzSrCRK7m3o90gysDVm",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Lazy"
   ],
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   }
  },
  {
   "cell_type":"code",
   "source":[
    "class WithLazy{\n",
    "    val prop = 2\n",
    "        get(){\n",
    "            println(\"Hit $field\")\n",
    "            return field\n",
    "        }\n",
    "\n",
    "    val lazyProp by lazy{\n",
    "        println(\"Hit lazy\")\n",
    "        2\n",
    "    }\n",
    "}"
   ],
   "execution_count":12,
   "outputs":[],
   "metadata":{
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     "node_id":"h0jgOzZDe8PiryzcHnNdBG",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "val withLazy = WithLazy()"
   ],
   "execution_count":13,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"5lXgZjAPOpwswgQpZIC0NO",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "withLazy.prop\n",
    "withLazy.prop\n",
    "withLazy.prop"
   ],
   "execution_count":14,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "Hit 2\n",
      "Hit 2\n",
      "Hit 2\n"
     ],
     "output_type":"stream"
    },
    {
     "data":{
      "text\/plain":[
       "2"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
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  },
  {
   "cell_type":"code",
   "source":[
    "withLazy.lazyProp\n",
    "withLazy.lazyProp\n",
    "withLazy.lazyProp"
   ],
   "execution_count":15,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "Hit lazy\n"
     ],
     "output_type":"stream"
    },
    {
     "data":{
      "text\/plain":[
       "2"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
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     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
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   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Builder"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"XYoUXQu8GD51C080v5thFD",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
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   }
  },
  {
   "cell_type":"code",
   "source":[
    "data class Buildable(\n",
    "    var a: Int = 1,\n",
    "    var b: Int = 2,\n",
    "    var c: Int = 3\n",
    "){\n",
    "    fun setABC(value: Int){\n",
    "        a = value\n",
    "        b = value\n",
    "        c = value\n",
    "    }\n",
    "}\n",
    "\n",
    "\/\/ Buildable.builder()\n",
    "\/\/     .setA(1)\n",
    "\/\/     .setB(2)\n",
    "\/\/     .setC(3)\n",
    "\/\/     .setABC(1)\n",
    "\/\/     .build()"
   ],
   "execution_count":7,
   "outputs":[],
   "metadata":{
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     "node_id":"nlm610q2oEsKlSDE1pXtkG",
     "type":"CODE",
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     "hide_output_from_viewers":true
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   }
  },
  {
   "cell_type":"code",
   "source":[
    "Buildable(b = 5)"
   ],
   "execution_count":8,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "Buildable(a=1, b=5, c=3)"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
   "metadata":{
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     "type":"CODE",
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     "hide_output_from_viewers":true
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   }
  },
  {
   "cell_type":"code",
   "source":[
    "Buildable().apply { \n",
    "    a = 1\n",
    "    setABC(a + b + c)\n",
    "}"
   ],
   "execution_count":9,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "Buildable(a=6, b=6, c=6)"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"hJnD2AzKDTgYkrZoyf31Hd",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "fun Buildable(block: Buildable.()-> Unit): Buildable = Buildable().apply(block)\n",
    "\n",
    "Buildable{ \n",
    "    a = 1\n",
    "    setABC(a + b + c)\n",
    "}"
   ],
   "execution_count":11,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "Buildable(a=6, b=6, c=6)"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"eybgzzEc7H4Px2nL7CKvvt",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Multiton"
   ],
   "attachments":{},
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     "type":"MD",
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    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class Multiton private constructor(val name: String){\n",
    "    init{\n",
    "        println(\"Multiton $name created\")\n",
    "    }\n",
    "    \n",
    "    companion object {\n",
    "        private val cache = HashMap<String, Multiton>()\n",
    "\n",
    "        fun resolve(name: String) = cache.getOrPut(name){Multiton(name)}\n",
    "    }\n",
    "}"
   ],
   "execution_count":16,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"jWHHMghzB2djqbkxMUA6Tx",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "Multiton.resolve(\"a\")\n",
    "Multiton.resolve(\"a\")\n",
    "Multiton.resolve(\"b\")\n",
    "Multiton.resolve(\"a\")"
   ],
   "execution_count":17,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "Multiton a created\n",
      "Multiton b created\n"
     ],
     "output_type":"stream"
    },
    {
     "data":{
      "text\/plain":[
       "Line_61_jupyter$Multiton@5271dd0f"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
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     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "Multiton(\"v\")"
   ],
   "execution_count":18,
   "outputs":[
    {
     "name":"stderr",
     "text":[
      "Line_67.jupyter.kts (1:1 - 9) Cannot access '<init>': it is private in 'Multiton'"
     ],
     "output_type":"stream"
    },
    {
     "ename":"Syntax Error",
     "evalue":"Syntax Error: Cannot access '<init>': it is private in 'Multiton'",
     "traceback":[
      "\u001b[0;31m---------------------------------------------------------------------------",
      "Traceback (most recent call last)",
      "Syntax Error: Cannot access '<init>': it is private in 'Multiton'"
     ],
     "output_type":"error"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"q7uzHnibwUrfQT3IbMmcce",
     "type":"CODE",
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     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "sealed interface SealedMultiton{\n",
    "    object A: SealedMultiton\n",
    "    object B: SealedMultiton\n",
    "    class Custom(val body: String): SealedMultiton\n",
    "}\n",
    "\n",
    "fun evaluateSealedMultiton(sealed: SealedMultiton) = when(sealed){\n",
    "    is SealedMultiton.A-> println(\"A\")\n",
    "    is SealedMultiton.B-> println(\"B\")\n",
    "    is SealedMultiton.Custom -> println(sealed.body)\n",
    "}"
   ],
   "execution_count":24,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"6GgWOmtJcF5yzCoPf7PbRE",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Adapter"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"YfxaLKY0BwQjCnS48Fkh3z",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "val array = doubleArrayOf(1.0,2.0)\n",
    "val list = listOf(1.0,2.0)\n",
    "\n",
    "\n",
    "fun consumeList(l: List<Double>){\n",
    "    println(l)\n",
    "}\n",
    "\n",
    "fun convertArrayToList(array: DoubleArray): List<Double> = array.asList()\/\/List(array.size){i -> array[i]}\n",
    "\n",
    "consumeList(convertArrayToList(array))"
   ],
   "execution_count":25,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "[1.0, 2.0]\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"0r5gCS5ICD5utC3vtYhbOb",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Decorator?"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"jsc3UoWftQEDJuUInDWIpe",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "@JvmInline\n",
    "value class EMail(val address: String)\n",
    "\n",
    "fun EMail.validate(): Boolean = TODO()\n",
    "\n",
    "val EMail.server get() = address.substringAfter(\"@\")"
   ],
   "execution_count":27,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"cML7IAfXcFt8Aab6PWZ0z0",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Delegate"
   ],
   "attachments":{},
   "metadata":{
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     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class ValueHolder{\n",
    "    var value = 2\n",
    "\n",
    "    fun printValue(){\n",
    "        println(value)\n",
    "    }\n",
    "}\n",
    "\n",
    "ValueHolder().apply { value = 6 }.printValue()"
   ],
   "execution_count":28,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "6\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
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   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "Bad example"
   ],
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   }
  },
  {
   "cell_type":"code",
   "source":[
    "class ModifiedValueHolder: ValueHolder(){\n",
    "    override fun printValue(){\n",
    "        print(\"value = \")\n",
    "        super.printValue()\n",
    "    }\n",
    "}\n",
    "\n",
    "ModifiedValueHolder().apply { value = 6 }.printValue()"
   ],
   "execution_count":29,
   "outputs":[
    {
     "name":"stderr",
     "text":[
      "Line_141.jupyter.kts (1:28 - 39) This type is final, so it cannot be inherited from\n",
      "Line_141.jupyter.kts (2:5 - 13) 'printValue' in 'ValueHolder' is final and cannot be overridden\n",
      "Line_141.jupyter.kts (8:31 - 36) Unresolved reference. None of the following candidates is applicable because of receiver type mismatch: \n",
      "public final var value: Int defined in Line_141_jupyter.ModifiedValueHolder"
     ],
     "output_type":"stream"
    },
    {
     "ename":"Syntax Error",
     "evalue":"Syntax Error: This type is final, so it cannot be inherited from",
     "traceback":[
      "\u001b[0;31m---------------------------------------------------------------------------",
      "Traceback (most recent call last)",
      "Syntax Error: This type is final, so it cannot be inherited from"
     ],
     "output_type":"error"
    }
   ],
   "metadata":{
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     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class GoodValueHolder(val valueHolder: ValueHolder = ValueHolder()){\n",
    "\n",
    "    var value by valueHolder::value\n",
    "\n",
    "    fun printValue(){\n",
    "        print(\"value = \")\n",
    "        valueHolder.printValue()\n",
    "    }\n",
    "}\n",
    "GoodValueHolder().apply { value = 6 }.printValue()"
   ],
   "execution_count":27,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "value = 6\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"OHLrIGtjkN2XQjYacDM8ut",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class CompositeValueHolder(\n",
    "    val a: ValueHolder,\n",
    "    val b: ValueHolder\n",
    "){\n",
    "    fun printValue(){\n",
    "        print(\"a = \")\n",
    "        a.printValue()\n",
    "        println()\n",
    "        print(\"b = \")\n",
    "        a.printValue()\n",
    "\n",
    "    }\n",
    "}"
   ],
   "execution_count":null,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"fdNq2E5bTa6zarGwDDqQFj",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class Id(val value: String)"
   ],
   "execution_count":43,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"3OCnDlksXhltJds6fY0L7v",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "Id(\"d3d\").value"
   ],
   "execution_count":44,
   "outputs":[
    {
     "data":{
      "text\/plain":[
       "d3d"
      ]
     },
     "metadata":{},
     "output_type":"display_data"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"MjDAABWvcpMQLzBFN4x91C",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "Id(\"fff\").length"
   ],
   "execution_count":41,
   "outputs":[
    {
     "name":"stderr",
     "text":[
      "Line_154.jupyter-kts (1:11 - 17) Unresolved reference: length"
     ],
     "output_type":"stream"
    },
    {
     "ename":"Syntax Error",
     "evalue":"Syntax Error: Unresolved reference: length",
     "traceback":[
      "\u001b[0;31m---------------------------------------------------------------------------",
      "Traceback (most recent call last)",
      "Syntax Error: Unresolved reference: length"
     ],
     "output_type":"error"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"525C4u3URrTwsBeZ2sTLud",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Proxy"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"NwAoDBrhHGOMQkkInhobM1",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class StringProxy(val string: String): CharSequence by string{\n",
    "    override fun get(index: Int): Char{\n",
    "        return if(index < 0)  '!' else string[index]\n",
    "    }\n",
    "}"
   ],
   "execution_count":30,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"x3XnwlrqMLxwzwughZSmqw",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "val proxy = StringProxy(\"dddd\")\n",
    "\n",
    "println(proxy[0])\n",
    "println(proxy[-1])"
   ],
   "execution_count":31,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "d\n",
      "!\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"ZAprJIO0gNiM69lJSMgPVt",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Observer"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"xF2sXItrdeH2pbwchAI8UQ",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class ObservableValueHolder(defaultValue: Int, val callback: (Int) -> Unit){\n",
    "    var value: Int = defaultValue\n",
    "        set(value){\n",
    "            field = value\n",
    "            callback(value)\n",
    "        }\n",
    "}"
   ],
   "execution_count":1,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"wLHHws3VLVqGyjA3YIdnaa",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "val holder = ObservableValueHolder(1){\n",
    "    println(\"Changed value = $it\")\n",
    "}\n",
    "holder.value = 6\n",
    "holder.value = 7"
   ],
   "execution_count":2,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "Changed value = 6\n",
      "Changed value = 7\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"pAG4a8kqIeaClaAtAOOkwJ",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Visitor"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"0dpe5zY5a0RQW1ueDfxV4W",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "### Classic visitor"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"nePxZT9HQTU2lEhESlhVly",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "interface Structure\n",
    "\n",
    "class StringStructure(val string: String): Structure\n",
    "\n",
    "class IntStructure(val int: Int): Structure\n",
    "\n",
    "class StructureList(val content: List<Structure>): Structure"
   ],
   "execution_count":13,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"Wo26AfHjCt8mlaZ2yIMcOm",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "fun interface StructureVisitor{\n",
    "    fun visit(structure: Structure): Unit\n",
    "}\n",
    "\n",
    "val myStructureVisitor = object: StructureVisitor{\n",
    "    override fun visit(structure: Structure){\n",
    "        when(structure){\n",
    "            is StringStructure -> println(\"It is a StringStructure with value ${structure.string}\")\n",
    "            is IntStructure -> println(\"It is a IntStructure with value ${structure.int}\")\n",
    "            is StructureList -> structure.content.forEach{ visit(it) }\n",
    "            else -> println(\"I don't know what it is\")\n",
    "        }\n",
    "    }\n",
    "}\n",
    "\n",
    "fun StructureList.visit(visitor: StructureVisitor){\n",
    "    visitor.visit(this)\n",
    "}"
   ],
   "execution_count":17,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"7ga1xsthc8oovIBmcC8Cg9",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "fun List<Structure>.asStructure() = StructureList(this)\n",
    "\n",
    "@JvmName(\"stringsAsStruct\")\n",
    "fun List<String>.asStructure() = StructureList(map{StringStructure(it)})\n",
    "\n",
    "val structureList = StructureList(\n",
    "    listOf(\n",
    "        StringStructure(\"ddd\"),\n",
    "        IntStructure(2),    \n",
    "        IntStructure(7),\n",
    "        listOf(\"aaa\", \"bbb\").asStructure()\n",
    "    )\n",
    ")\n",
    "\n",
    "structureList.visit(myStructureVisitor)"
   ],
   "execution_count":24,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "It is a StringStructure with value ddd\n",
      "It is a IntStructure with value 2\n",
      "It is a IntStructure with value 7\n",
      "It is a StringStructure with value aaa\n",
      "It is a StringStructure with value bbb\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"lAzMMN1L3TmQl2cVxi36ED",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "### Kotlin idiomatic visiting"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"wvN4YCDwzYUDQfXA7IoRUr",
     "type":"MD",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "sealed interface SealedStructure\n",
    "\n",
    "class StringSealedStructure(val string: String): SealedStructure\n",
    "\n",
    "class IntSealedStructure(val int: Int): SealedStructure"
   ],
   "execution_count":27,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"GjXhhTAsHL0AUcEzmuypK1",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "fun List<SealedStructure>.visit(visitor: (SealedStructure) -> Unit){\n",
    "    forEach(visitor)\n",
    "}"
   ],
   "execution_count":28,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"p58da7MiEz4NeXbk2ZUyiz",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "val sealedStructureList = listOf<SealedStructure>(\n",
    "    StringSealedStructure(\"ddd\"),\n",
    "    IntSealedStructure(2),    \n",
    "    IntSealedStructure(7),\n",
    ")\n",
    "\n",
    "sealedStructureList.visit{ structure ->\n",
    "    when(structure){\n",
    "        is StringSealedStructure -> println(\"It is a StringSealedStructure with value ${structure.string}\")\n",
    "        is IntSealedStructure -> println(\"It is a IntSealedStructure with value ${structure.int}\")\n",
    "        else -> {} \/\/ why is that?\n",
    "    }\n",
    "}"
   ],
   "execution_count":30,
   "outputs":[
    {
     "name":"stderr",
     "text":[
      "Line_206.jupyter.kts (8:5 - 9) 'when' expression must be exhaustive, add necessary 'else' branch"
     ],
     "output_type":"stream"
    },
    {
     "ename":"Syntax Error",
     "evalue":"Syntax Error: 'when' expression must be exhaustive, add necessary 'else' branch",
     "traceback":[
      "\u001b[0;31m---------------------------------------------------------------------------",
      "Traceback (most recent call last)",
      "Syntax Error: 'when' expression must be exhaustive, add necessary 'else' branch"
     ],
     "output_type":"error"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"aCfKGNanITfEocl3N0T0Ce",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[],
   "execution_count":null,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"EmfBYCTjDyjeCP4LqTIyFg",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"markdown",
   "source":[
    "# Observer"
   ],
   "attachments":{},
   "metadata":{
    "datalore":{
     "node_id":"Observer",
     "type":"MD",
     "hide_input_from_viewers":false,
     "hide_output_from_viewers":false,
     "sheet_delimiter":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "import kotlin.properties.Delegates\n",
    "\n",
    "class ObservableHolder{\n",
    "    var observable: Int by Delegates.observable<Int>(1){ property, oldValue, newValue ->\n",
    "        println(\"${property.name} $newValue\")\n",
    "    }\n",
    "}"
   ],
   "execution_count":8,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"h2OYBThfWjdp7hhteNH2Lt",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "val holder = ObservableHolder()\n",
    "\n",
    "holder.observable = 5"
   ],
   "execution_count":9,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "observable 5\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"pAzvJyJubYwBrzqNmGLAMj",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[
    "class Response(val header: String, val body: () -> String ){\n",
    "    fun onRead(callback: (String) -> Unit){\n",
    "        callback(body())\n",
    "    }\n",
    "}\n",
    "\n",
    "class Call(val request: String, val onResponse: (Response) -> Unit){\n",
    "    fun start(){\n",
    "        onResponse(Response(\"header\"){\"body\"})\n",
    "    }\n",
    "}\n",
    "\n",
    "Call(\"spc\"){ response->\n",
    "    println(response.header)\n",
    "    response.onRead{ body->\n",
    "        println(body)\n",
    "    }\n",
    "}.start()"
   ],
   "execution_count":12,
   "outputs":[
    {
     "name":"stdout",
     "text":[
      "header\n",
      "body\n"
     ],
     "output_type":"stream"
    }
   ],
   "metadata":{
    "datalore":{
     "node_id":"z4D2hzOyzy2Dmpi1QbKMqf",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  },
  {
   "cell_type":"code",
   "source":[],
   "execution_count":null,
   "outputs":[],
   "metadata":{
    "datalore":{
     "node_id":"QlpqRBkqqUHN2CUAm2hP3H",
     "type":"CODE",
     "hide_input_from_viewers":true,
     "hide_output_from_viewers":true
    }
   }
  }
 ],
 "metadata":{
  "kernelspec":{
   "display_name":"Kotlin",
   "language":"kotlin",
   "name":"kotlin"
  },
  "datalore":{
   "computation_mode":"JUPYTER",
   "package_manager":"pip",
   "base_environment":"default",
   "packages":[],
   "report_row_ids":[],
   "version":3
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 },
 "nbformat":4,
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}