api days notebook

worldline · Dec 3, 2024 · 6b3341e · 6b3341e
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diff --git a/material/conferences/2024-12-04-apidays/.gitignore b/material/conferences/2024-12-04-apidays/.gitignore
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+.idea/
diff --git a/material/conferences/2024-12-04-apidays/api-days2024.ipynb b/material/conferences/2024-12-04-apidays/api-days2024.ipynb
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+{
+ "cells": [
+  {
+   "metadata": {},
+   "cell_type": "markdown",
+   "source": "# Idiomatic Kotlin @ API Days Paris 2024"
+  },
+  {
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2024-12-03T23:23:52.926394100Z",
+     "start_time": "2024-12-03T23:23:52.833072600Z"
+    }
+   },
+   "cell_type": "code",
+   "source": [
+    "data class Event(val name: String, val year:Int) // One line class\n",
+    "val event = Event(\"API Days\", 2024)\n",
+    "println(event) // To string implemented out of the box\n",
+    "println(\"Hello ${event.name}\") // String template"
+   ],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Event(name=API Days, year=2024)\r\n",
+      "Hello API Days\r\n"
+     ]
+    }
+   ],
+   "execution_count": 12
+  },
+  {
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2024-12-03T23:23:53.033397Z",
+     "start_time": "2024-12-03T23:23:52.947644900Z"
+    }
+   },
+   "cell_type": "code",
+   "source": [
+    "// Extension function: add a method to a class without inhetitance\n",
+    "fun String.randomCase(): String {\n",
+    "    // If expression\n",
+    "    return if (Math.random() > 0.5) uppercase() else lowercase()\n",
+    "}\n",
+    "println(event.name.randomCase())"
+   ],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "API DAYS\r\n"
+     ]
+    }
+   ],
+   "execution_count": 13
+  },
+  {
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2024-12-03T23:23:53.160407300Z",
+     "start_time": "2024-12-03T23:23:53.047728100Z"
+    }
+   },
+   "cell_type": "code",
+   "source": [
+    "// Default values for arguments\n",
+    "fun String.randomCaseChance(chance: Double = 0.5, offset: Int = 0) =\n",
+    "    // Single-expression functions with = (return type is inferred)\n",
+    "    (if (Math.random() > chance) uppercase() else lowercase()).drop(offset)\n",
+    "// Argument labels\n",
+    "println(event.name.randomCaseChance(offset = 3))\n",
+    "println(event.name.randomCaseChance(\n",
+    "    offset = 2,\n",
+    "    chance = 0.9,\n",
+    "    )\n",
+    ")"
+   ],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      " DAYS\r\n",
+      "i days\r\n"
+     ]
+    }
+   ],
+   "execution_count": 14
+  },
+  {
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2024-12-03T23:23:53.264804800Z",
+     "start_time": "2024-12-03T23:23:53.171326300Z"
+    }
+   },
+   "cell_type": "code",
+   "source": [
+    "// Functions are 1st class citizen\n",
+    "fun String.transformToInt(transformer: (String) -> Int) = transformer(this)\n",
+    "// return is optionnal (in many situations)\n",
+    "val count0 = event.name.transformToInt({ s -> s.length })\n",
+    "// Parenthesis can be omitted for last lambda\n",
+    "// \"it\" is implicit for single-argument lambdas\n",
+    "val count = event.name.transformToInt { it.length }\n",
+    "println(count)"
+   ],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "8\r\n"
+     ]
+    }
+   ],
+   "execution_count": 15
+  },
+  {
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2024-12-03T23:23:53.588578700Z",
+     "start_time": "2024-12-03T23:23:53.424789800Z"
+    }
+   },
+   "cell_type": "code",
+   "source": [
+    "fun String.transformToString(transformer: String.() -> String) = transformer(this)\n",
+    "// String.() -> String means that the lambda has access to the string as \"this\"\n",
+    "val uppercased0 = event.name.transformToString { this.uppercase() }\n",
+    "// We usually omit this. This is the building block of DSLs (Domain Specific languages)\n",
+    "val uppercased = event.name.transformToString { uppercase() }\n",
+    "print(\"Uppercased: $uppercased\")"
+   ],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "Uppercased: API DAYS"
+     ]
+    }
+   ],
+   "execution_count": 16
+  },
+  {
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2024-12-03T23:23:53.834073100Z",
+     "start_time": "2024-12-03T23:23:53.598859900Z"
+    }
+   },
+   "cell_type": "code",
+   "source": [
+    "// Filter, map, reduce out of the box\n",
+    "println(\n",
+    "    event.name.map {\n",
+    "        if (Math.random() > 0.5) it.uppercaseChar() else it.lowercaseChar()\n",
+    "    }.joinToString()\n",
+    ")\n",
+    "// More operators available\n",
+    "println(\n",
+    "    event.name.zip(\"2024\") { left, right -> \"$left/$right\" }\n",
+    ")"
+   ],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "A, p, i,  , d, a, Y, s\r\n",
+      "[A/2, P/0, I/2,  /4]\r\n"
+     ]
+    }
+   ],
+   "execution_count": 17
+  },
+  {
+   "metadata": {
+    "ExecuteTime": {
+     "end_time": "2024-12-03T23:23:54.122576Z",
+     "start_time": "2024-12-03T23:23:53.854138200Z"
+    }
+   },
+   "cell_type": "code",
+   "source": [
+    "// ? Means that the argument can be null\n",
+    "fun getUppercaseName(dev: Map<String, String>?): String {\n",
+    "    if (dev == null){\n",
+    "        return \"NONE\"\n",
+    "    }\n",
+    "    // Here dev is casted to Map<String, String>\n",
+    "    // ?: is the elvis operator\n",
+    "    return (dev[\"name\"] ?: \"NONE\").uppercase()\n",
+    "}\n",
+    "fun getUppercaseNameSe(dev: Map<String, String>?) = dev?.get(\"name\")?.uppercase() ?: \"NONE\"\n",
+    "// Kotlin guarantees NPE free code at compile time (unless you use !!)\n",
+    "val dev = mapOf(\"name\" to \"Yassine\", \"Event\" to event.name)\n",
+    "println(dev)\n",
+    "println(getUppercaseName(dev))\n",
+    "println(getUppercaseNameSe(dev))"
+   ],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "{name=Yassine, Event=API Days}\r\n",
+      "YASSINE\r\n",
+      "YASSINE\r\n"
+     ]
+    }
+   ],
+   "execution_count": 18
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Kotlin",
+   "language": "kotlin",
+   "name": "kotlin"
+  },
+  "language_info": {
+   "name": "kotlin",
+   "version": "1.9.23",
+   "mimetype": "text/x-kotlin",
+   "file_extension": ".kt",
+   "pygments_lexer": "kotlin",
+   "codemirror_mode": "text/x-kotlin",
+   "nbconvert_exporter": ""
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}