{"id":1341,"date":"2025-03-24T08:52:19","date_gmt":"2025-03-23T23:52:19","guid":{"rendered":"https:\/\/dexall.co.jp\/articles\/?p=1341"},"modified":"2025-03-24T08:52:19","modified_gmt":"2025-03-23T23:52:19","slug":"%e3%80%90%e4%bf%9d%e5%ad%98%e7%89%88%e3%80%91ruby%e3%81%a7nil%e3%82%92%e5%ae%89%e5%85%a8%e3%81%ab%e6%89%b1%e3%81%869%e3%81%a4%e3%81%ae%e5%ae%9f%e8%b7%b5%e3%83%86%e3%82%af%e3%83%8b%e3%83%83%e3%82%af","status":"publish","type":"post","link":"https:\/\/dexall.co.jp\/articles\/?p=1341","title":{"rendered":"\u3010\u4fdd\u5b58\u7248\u3011Ruby\u3067Nil\u3092\u5b89\u5168\u306b\u6271\u30469\u3064\u306e\u5b9f\u8df5\u30c6\u30af\u30cb\u30c3\u30af &#8211; \u73fe\u5f79\u30a8\u30f3\u30b8\u30cb\u30a2\u304c\u89e3\u8aac"},"content":{"rendered":"\n<div class=\"toc\"><br \/>\n<b>Warning<\/b>:  Undefined array key \"is_admin\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>116<\/b><br \/>\n<br \/>\n<b>Warning<\/b>:  Undefined array key \"is_category_top\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>121<\/b><br \/>\n<br \/>\n<b>Warning<\/b>:  Undefined array key \"is_top\" in <b>\/home\/xs392991\/dexall.co.jp\/public_html\/articles\/wp-content\/themes\/sango-theme\/library\/gutenberg\/dist\/classes\/Toc.php<\/b> on line <b>128<\/b><br \/>\n    <div id=\"toc_container\" class=\"sgb-toc--bullets js-smooth-scroll\" data-dialog-title=\"\u76ee\u6b21\">\n      <p class=\"toc_title\">\u76ee\u6b21 <\/p>\n      <ul class=\"toc_list\">  <li class=\"first\">    <a href=\"#i-0\">Ruby\u306b\u304a\u3051\u308bnil\u3068\u306f\uff1f\u57fa\u790e\u304b\u3089\u5b8c\u5168\u7406\u89e3<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-1\">nil\u306fRuby\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8 \u2013 NilClass\u306e\u7279\u5fb4\u3068\u4ed5\u69d8<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-3\">\u306a\u305cnil\u304c\u554f\u984c\u3092\u5f15\u304d\u8d77\u3053\u3059\u306e\u304b \u2013 \u5178\u578b\u7684\u306a\u30a8\u30e9\u30fc\u30d1\u30bf\u30fc\u30f3<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-9\">nil\u306b\u3088\u308b\u30a8\u30e9\u30fc\u3092\u9632\u3050\u5b9f\u8df5\u30c6\u30af\u30cb\u30c3\u30af<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-10\">\u5b89\u5168\u306a\u30e1\u30bd\u30c3\u30c9\u30c1\u30a7\u30fc\u30f3&amp;try!\u30e1\u30bd\u30c3\u30c9\u306e\u6d3b\u7528\u6cd5<\/a>      <\/li>      <li>        <a href=\"#i-13\">nil?\u3068blank?\u306e\u4f7f\u3044\u5206\u3051\u3067\u5805\u7262\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-16\">\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u8a2d\u5b9a\u3057\u3066nil\u3092\u56de\u907f\u3059\u308b\u8ce2\u3044\u65b9\u6cd5<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-21\">ActiveRecord\u3067\u306enil\u5bfe\u7b56\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-22\">\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\u3067nil\u3092\u5236\u5fa1\u3059\u308b\u52b9\u679c\u7684\u306a\u65b9\u6cd5<\/a>      <\/li>      <li>        <a href=\"#i-25\">nil\u3092\u8003\u616e\u3057\u305f\u30b9\u30b3\u30fc\u30d7\u306e\u66f8\u304d\u65b9<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-28\">\u95a2\u9023\u4ed8\u3051\u3067\u767a\u751f\u3059\u308bnil\u306e\u5bfe\u51e6\u6cd5<\/a>      <\/li>    <\/ul>  <\/li>  <li>    <a href=\"#i-31\">\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u610f\u8b58\u3057\u305fnil\u51e6\u7406\u306e\u6700\u9069\u5316<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-32\">\u30e1\u30e2\u30ea\u52b9\u7387\u3092\u8003\u616e\u3057\u305fnil\u5224\u5b9a\u306e\u5b9f\u88c5<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-35\">nil\u30ac\u30fc\u30c9\u7bc0\u306b\u3088\u308b\u51e6\u7406\u306e\u9ad8\u901f\u5316\u30c6\u30af\u30cb\u30c3\u30af<\/a>      <\/li>    <\/ul>  <\/li>  <li class=\"last\">    <a href=\"#i-38\">\u5b9f\u8df5\u7684\u306a\u30b3\u30fc\u30c9\u4f8b\u3067\u5b66\u3076nil\u5bfe\u7b56\u30d1\u30bf\u30fc\u30f3<\/a>    <ul class=\"menu_level_1\">      <li class=\"first\">        <a href=\"#i-39\">\u30e6\u30fc\u30b6\u30fc\u60c5\u5831\u53d6\u5f97\u6642\u306enil\u5bfe\u7b56\u5b9f\u88c5\u4f8b<\/a>      <\/li>      <li>        <a href=\"#i-41\">API\u30ec\u30b9\u30dd\u30f3\u30b9\u51e6\u7406\u3067\u306enil\u5b89\u5168\u6027\u306e\u78ba\u4fdd<\/a>      <\/li>      <li class=\"last\">        <a href=\"#i-43\">\u30d0\u30c3\u30c1\u51e6\u7406\u3067\u306e\u5805\u7262\u306anil\u51e6\u7406\u306e\u5b9f\u88c5<\/a>      <\/li>    <\/ul>  <\/li><\/ul>\n      <a href=\"#\" class=\"sgb-toc-button js-toc-button\" rel=\"nofollow\" data-open-dialog=\"true\"><i class=\"fa fa-list\"><\/i><span class=\"sgb-toc-button__text\">\u76ee\u6b21\u3078<\/span><\/a>\n    <\/div><\/div><h2 class=\"wp-block-heading\" id=\"i-0\">Ruby\u306b\u304a\u3051\u308bnil\u3068\u306f\uff1f\u57fa\u790e\u304b\u3089\u5b8c\u5168\u7406\u89e3<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-1\">nil\u306fRuby\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8 \u2013 NilClass\u306e\u7279\u5fb4\u3068\u4ed5\u69d8<\/h3>\n\n\n\n<p>Ruby\u306b\u304a\u3044\u3066\u3001<code>nil<\/code>\u306f\u7279\u5225\u306a\u610f\u5473\u3092\u6301\u3064\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3067\u3059\u3002\u4ed6\u306e\u8a00\u8a9e\u3067\u306f<code>null<\/code>\u3084<code>None<\/code>\u3068\u547c\u3070\u308c\u308b\u6982\u5ff5\u306b\u76f8\u5f53\u3057\u307e\u3059\u304c\u3001Ruby\u306e<code>nil<\/code>\u306b\u306f\u72ec\u81ea\u306e\u7279\u5fb4\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-2\">nil\u306e\u57fa\u672c\u7684\u306a\u7279\u5fb4<\/h4>\n\n\n\n<ol class=\"wp-block-list\">\n<li><code>nil<\/code>\u306f<code>NilClass<\/code>\u30af\u30e9\u30b9\u306e\u552f\u4e00\u306e\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9<\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># nil\u306e\u578b\u3092\u78ba\u8a8d\np nil.class  #=&gt; NilClass\n\n# nil\u306f\u30b7\u30f3\u30b0\u30eb\u30c8\u30f3\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\np nil.object_id  #=&gt; 8\np nil.object_id == nil.object_id  #=&gt; true<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list\">\n<li>\u771f\u507d\u5024\u3068\u3057\u3066\u306e<code>nil<\/code><\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># nil\u3068false\u306f\u507d\u3068\u3057\u3066\u8a55\u4fa1\u3055\u308c\u308b\nif nil\n  puts \"This won't be printed\"\nend\n\n# nil\u3068false\u306f\u7570\u306a\u308b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\np nil == false    #=&gt; false\np nil.nil?        #=&gt; true\np false.nil?      #=&gt; false<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-3\">\u306a\u305cnil\u304c\u554f\u984c\u3092\u5f15\u304d\u8d77\u3053\u3059\u306e\u304b \u2013 \u5178\u578b\u7684\u306a\u30a8\u30e9\u30fc\u30d1\u30bf\u30fc\u30f3<\/h3>\n\n\n\n<p><code>nil<\/code>\u306b\u95a2\u9023\u3059\u308b\u554f\u984c\u306f\u3001\u4e3b\u306b\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u30b7\u30c1\u30e5\u30a8\u30fc\u30b7\u30e7\u30f3\u3067\u767a\u751f\u3057\u307e\u3059\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-4\">1. \u30e1\u30bd\u30c3\u30c9\u547c\u3073\u51fa\u3057\u30a8\u30e9\u30fc<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># NoMethodError\u306e\u4f8b\nuser = nil\nuser.name  #=&gt; NoMethodError: undefined method `name' for nil:NilClass\n\n# \u914d\u5217\u8981\u7d20\u3078\u306e\u30a2\u30af\u30bb\u30b9\narray = nil\narray[0]   #=&gt; NoMethodError: undefined method `[]' for nil:NilClass<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-5\">2. \u4e88\u671f\u305b\u306cnil\u4f1d\u64ad<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class User\n  def address\n    nil\n  end\nend\n\nuser = User.new\n# nil\u304c\u4f1d\u64ad\u3057\u3066\u30a8\u30e9\u30fc\u306b\u306a\u308b\u30b1\u30fc\u30b9\ncity_name = user.address.city.name  #=&gt; NoMethodError<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-6\">3. \u8a08\u7b97\u30a8\u30e9\u30fc<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">value = nil\nresult = value + 1  #=&gt; NoMethodError: undefined method `+' for nil:NilClass<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-7\">nil\u304c\u767a\u751f\u3059\u308b\u4e00\u822c\u7684\u306a\u72b6\u6cc1<\/h4>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u304b\u3089\u306e\u30ec\u30b3\u30fc\u30c9\u53d6\u5f97<\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">user = User.find_by(id: 999)  # \u5b58\u5728\u3057\u306a\u3044ID\u306e\u5834\u5408nil\u304c\u8fd4\u308b<\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list\">\n<li>\u914d\u5217\u3084\u30cf\u30c3\u30b7\u30e5\u306e\u8981\u7d20\u30a2\u30af\u30bb\u30b9<\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">array = [1, 2, 3]\narray[5]  #=&gt; nil  # \u5b58\u5728\u3057\u306a\u3044\u30a4\u30f3\u30c7\u30c3\u30af\u30b9\u306b\u30a2\u30af\u30bb\u30b9\n\nhash = { a: 1 }\nhash[:b]  #=&gt; nil  # \u5b58\u5728\u3057\u306a\u3044\u30ad\u30fc\u306b\u30a2\u30af\u30bb\u30b9<\/pre>\n\n\n\n<ol start=\"3\" class=\"wp-block-list\">\n<li>\u6b63\u898f\u8868\u73fe\u30de\u30c3\u30c1\u30f3\u30b0<\/li>\n<\/ol>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\"hello\" =~ \/xyz\/  #=&gt; nil  # \u30de\u30c3\u30c1\u3057\u306a\u3044\u5834\u5408<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-8\">nil\u306e\u7279\u6027\u3092\u6d3b\u304b\u3057\u305f\u6a5f\u80fd<\/h4>\n\n\n\n<p><code>nil<\/code>\u306f\u554f\u984c\u3092\u5f15\u304d\u8d77\u3053\u3059\u539f\u56e0\u3068\u306a\u308a\u307e\u3059\u304c\u3001\u9069\u5207\u306b\u4f7f\u7528\u3059\u308b\u3053\u3068\u3067\u4fbf\u5229\u306a\u6a5f\u80fd\u3082\u63d0\u4f9b\u3057\u307e\u3059\uff1a<\/p>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># nil\u5408\u4f53\u6f14\u7b97\u5b50\u306e\u6d3b\u7528\nconfig = nil\ntimeout = config&amp;.timeout || 30  # \u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u306e\u8a2d\u5b9a\n\n# \u6761\u4ef6\u5206\u5c90\u3067\u306e\u6d3b\u7528\nif result = some_calculation\n  # \u7d50\u679c\u304c\u5b58\u5728\u3059\u308b\u5834\u5408\u306e\u51e6\u7406\nelse\n  # nil\u306e\u5834\u5408\u306e\u51e6\u7406\nend<\/pre>\n\n\n\n<p>\u3053\u306e\u3088\u3046\u306b\u3001<code>nil<\/code>\u306fRuby\u30d7\u30ed\u30b0\u30e9\u30df\u30f3\u30b0\u306b\u304a\u3044\u3066\u907f\u3051\u3066\u901a\u308c\u306a\u3044\u91cd\u8981\u306a\u6982\u5ff5\u3067\u3059\u3002\u9069\u5207\u306b\u6271\u3046\u3053\u3068\u3067\u3001\u3088\u308a\u5805\u7262\u306a\u30d7\u30ed\u30b0\u30e9\u30e0\u3092\u4f5c\u6210\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001\u5177\u4f53\u7684\u306a<code>nil<\/code>\u5bfe\u7b56\u306e\u5b9f\u8df5\u30c6\u30af\u30cb\u30c3\u30af\u306b\u3064\u3044\u3066\u89e3\u8aac\u3057\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-9\">nil\u306b\u3088\u308b\u30a8\u30e9\u30fc\u3092\u9632\u3050\u5b9f\u8df5\u30c6\u30af\u30cb\u30c3\u30af<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-10\">\u5b89\u5168\u306a\u30e1\u30bd\u30c3\u30c9\u30c1\u30a7\u30fc\u30f3&amp;try!\u30e1\u30bd\u30c3\u30c9\u306e\u6d3b\u7528\u6cd5<\/h3>\n\n\n\n<p>\u30e1\u30bd\u30c3\u30c9\u30c1\u30a7\u30fc\u30f3\u3067\u306e<code>nil<\/code>\u30a8\u30e9\u30fc\u3092\u9632\u3050\u305f\u3081\u306b\u3001Ruby\u3067\u306f\u8907\u6570\u306e\u52b9\u679c\u7684\u306a\u65b9\u6cd5\u304c\u7528\u610f\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-11\">&amp;.\u6f14\u7b97\u5b50\uff08\u307c\u3063\u3061\u6f14\u7b97\u5b50\uff09\u306e\u6d3b\u7528<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># \u5f93\u6765\u306e\u5b89\u5168\u3067\u306a\u3044\u65b9\u6cd5\nuser.address.city.name  # =&gt; nil\u306e\u5834\u5408NoMethodError\n\n# \u307c\u3063\u3061\u6f14\u7b97\u5b50\u3092\u4f7f\u7528\u3057\u305f\u5b89\u5168\u306a\u65b9\u6cd5\nuser&amp;.address&amp;.city&amp;.name  # =&gt; nil\u306e\u5834\u5408\u306fnil<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-12\">try!\u30e1\u30bd\u30c3\u30c9\u306e\u4f7f\u3044\u65b9<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># ActiveSupport\u5fc5\u8981\nrequire 'active_support\/all'\n\n# try\u30e1\u30bd\u30c3\u30c9\u306e\u57fa\u672c\u7684\u306a\u4f7f\u3044\u65b9\nuser.try!(:name)  # =&gt; \u30e1\u30bd\u30c3\u30c9\u304c\u5b58\u5728\u3057\u306a\u3044\u5834\u5408\u306fnil\n\n# \u30d6\u30ed\u30c3\u30af\u4ed8\u304d\u306etry\nuser.try! { |u| u.name.upcase }  # =&gt; \u5b89\u5168\u306b\u30e1\u30bd\u30c3\u30c9\u30c1\u30a7\u30fc\u30f3<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-13\">nil?\u3068blank?\u306e\u4f7f\u3044\u5206\u3051\u3067\u5805\u7262\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f<\/h3>\n\n\n\n<p><code>nil?<\/code>\u3068<code>blank?<\/code>\u306f\u4f3c\u3066\u3044\u308b\u3088\u3046\u3067\u7570\u306a\u308b\u7528\u9014\u304c\u3042\u308a\u307e\u3059\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-14\">nil?\u306e\u4f7f\u7528\u5834\u5408<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># \u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304cnil\u304b\u3069\u3046\u304b\u3092\u53b3\u5bc6\u306b\u5224\u5b9a\nvalue = nil\nvalue.nil?  # =&gt; true\n\nobject = Object.new\nobject.nil?  # =&gt; false<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-15\">blank?\u306e\u4f7f\u7528\u5834\u5408\uff08ActiveSupport\uff09<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># \u7a7a\u6587\u5b57\u3084\u30b9\u30da\u30fc\u30b9\u3082true\u3068\u3057\u3066\u6271\u3046\n\"\".blank?      # =&gt; true\n\" \".blank?     # =&gt; true\nnil.blank?     # =&gt; true\n[].blank?      # =&gt; true\n{}.blank?      # =&gt; true\n\n# present?\u306fblank?\u306e\u53cd\u5bfe\n\"hello\".present?  # =&gt; true\n\"\".present?      # =&gt; false<\/pre>\n\n\n\n<p>\u4f7f\u3044\u5206\u3051\u306e\u57fa\u6e96\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>nil?<\/code>: \u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304c\u53b3\u5bc6\u306b<code>nil<\/code>\u304b\u3069\u3046\u304b\u3092\u78ba\u8a8d\u3059\u308b\u5834\u5408<\/li>\n\n\n\n<li><code>blank?<\/code>: \u5024\u304c\u5b9f\u8cea\u7684\u306b\u7a7a\uff08empty\uff09\u304b\u3069\u3046\u304b\u3092\u78ba\u8a8d\u3059\u308b\u5834\u5408<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-16\">\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u8a2d\u5b9a\u3057\u3066nil\u3092\u56de\u907f\u3059\u308b\u8ce2\u3044\u65b9\u6cd5<\/h3>\n\n\n\n<p>\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u306e\u8a2d\u5b9a\u306b\u306f\u8907\u6570\u306e\u30c6\u30af\u30cb\u30c3\u30af\u304c\u3042\u308a\u307e\u3059\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-17\">||\u6f14\u7b97\u5b50\u306e\u6d3b\u7528<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># \u57fa\u672c\u7684\u306a\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u306e\u8a2d\u5b9a\nname = user_input || \"\u540d\u7121\u3057\u3055\u3093\"\n\n# \u30e1\u30bd\u30c3\u30c9\u3067\u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\ndef greeting(name = \"\u30b2\u30b9\u30c8\")\n  \"\u3053\u3093\u306b\u3061\u306f\u3001#{name}\u3055\u3093\"\nend<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-18\">nil\u5408\u4f53\u6f14\u7b97\u5b50\uff08<code>||=<\/code>\uff09\u306e\u4f7f\u7528<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># \u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u5909\u6570\u306e\u521d\u671f\u5316\u306b\u3088\u304f\u4f7f\u7528\nclass User\n  def cached_data\n    @cached_data ||= expensive_calculation\n  end\nend<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-19\">fetch \u30e1\u30bd\u30c3\u30c9\u306e\u6d3b\u7528<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># \u30cf\u30c3\u30b7\u30e5\u3067\u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u8a2d\u5b9a\nconfig = {}\ntimeout = config.fetch(:timeout, 30)  # \u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u306f30\n\n# \u30d6\u30ed\u30c3\u30af\u3092\u4f7f\u7528\u3057\u305f\u3088\u308a\u8907\u96d1\u306a\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\ntimeout = config.fetch(:timeout) { calculate_default_timeout }<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-20\">\u6761\u4ef6\u4ed8\u304d\u30c7\u30d5\u30a9\u30eb\u30c8\u5024<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">def process_user(user)\n  return \"\u30b2\u30b9\u30c8\u51e6\u7406\" if user.nil?\n  # \u901a\u5e38\u306e\u51e6\u7406\n  user.process\nend<\/pre>\n\n\n\n<p>\u3053\u308c\u3089\u306e\u30c6\u30af\u30cb\u30c3\u30af\u3092\u9069\u5207\u306b\u7d44\u307f\u5408\u308f\u305b\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5805\u7262\u306a\u30b3\u30fc\u30c9\u3092\u66f8\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u91cd\u8981\u306a\u306e\u306f\u3001<code>nil<\/code>\u3092\u5b8c\u5168\u306b\u6392\u9664\u3059\u308b\u306e\u3067\u306f\u306a\u304f\u3001\u9069\u5207\u306b\u7ba1\u7406\u3059\u308b\u3053\u3068\u3067\u3059\u3002<\/p>\n\n\n\n<p>\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001ActiveRecord\u3067\u306e\u5177\u4f53\u7684\u306a<code>nil<\/code>\u5bfe\u7b56\u306b\u3064\u3044\u3066\u8aac\u660e\u3057\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-21\">ActiveRecord\u3067\u306enil\u5bfe\u7b56\u30d9\u30b9\u30c8\u30d7\u30e9\u30af\u30c6\u30a3\u30b9<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-22\">\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\u3067nil\u3092\u5236\u5fa1\u3059\u308b\u52b9\u679c\u7684\u306a\u65b9\u6cd5<\/h3>\n\n\n\n<p>ActiveRecord\u3067\u306f\u3001\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\u3092\u4f7f\u7528\u3057\u3066<code>nil<\/code>\u5024\u306e\u767a\u751f\u3092\u672a\u7136\u306b\u9632\u3050\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-23\">\u57fa\u672c\u7684\u306apresence\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class User &lt; ApplicationRecord\n  # \u57fa\u672c\u7684\u306a\u5fc5\u9808\u30c1\u30a7\u30c3\u30af\n  validates :name, presence: true\n\n  # \u30ab\u30b9\u30bf\u30e0\u30e1\u30c3\u30bb\u30fc\u30b8\u4ed8\u304d\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\n  validates :email, presence: { message: '\u30e1\u30fc\u30eb\u30a2\u30c9\u30ec\u30b9\u3092\u5165\u529b\u3057\u3066\u304f\u3060\u3055\u3044' }\n\n  # \u6761\u4ef6\u4ed8\u304d\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\n  validates :phone, presence: true, if: :requires_phone?\n\n  private\n\n  def requires_phone?\n    customer_type == 'business'\n  end\nend<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-24\">\u95a2\u9023\u4ed8\u3051\u306e\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class Order &lt; ApplicationRecord\n  belongs_to :user\n  belongs_to :product\n\n  # belongs_to\u306f\u81ea\u52d5\u3067presence\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\u304c\u4ed8\u304f\n  # \u30aa\u30d7\u30b7\u30e7\u30ca\u30eb\u306b\u3059\u308b\u5834\u5408\u306f\u660e\u793a\u7684\u306b\u6307\u5b9a\n  belongs_to :coupon, optional: true\n\n  # \u8907\u6570\u306e\u95a2\u9023\u3092\u540c\u6642\u306b\u30c1\u30a7\u30c3\u30af\n  validates_associated :order_items\nend<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-25\">nil\u3092\u8003\u616e\u3057\u305f\u30b9\u30b3\u30fc\u30d7\u306e\u66f8\u304d\u65b9<\/h3>\n\n\n\n<p>\u30b9\u30b3\u30fc\u30d7\u3092\u5b9a\u7fa9\u3059\u308b\u969b\u306f\u3001<code>nil<\/code>\u5024\u306e\u53d6\u308a\u6271\u3044\u3092\u660e\u78ba\u306b\u3059\u308b\u3053\u3068\u304c\u91cd\u8981\u3067\u3059\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-26\">\u57fa\u672c\u7684\u306a\u30b9\u30b3\u30fc\u30d7\u30d1\u30bf\u30fc\u30f3<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class Product &lt; ApplicationRecord\n  # nil\u3092\u9664\u5916\u3059\u308b\u30b9\u30b3\u30fc\u30d7\n  scope :with_description, -&gt; { where.not(description: nil) }\n\n  # nil\u3092\u542b\u3080\u30b9\u30b3\u30fc\u30d7\n  scope :without_price, -&gt; { where(price: nil) }\n\n  # nil\u3068\u7a7a\u6587\u5b57\u3092\u4e21\u65b9\u51e6\u7406\u3059\u308b\u30b9\u30b3\u30fc\u30d7\n  scope :with_valid_name, -&gt; { where.not(name: [nil, '']) }\n\n  # \u8907\u96d1\u306a\u6761\u4ef6\u3067\u306enil\u8003\u616e\n  scope :active_or_nil_status, -&gt; { \n    where(status: ['active', nil])\n  }\nend<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-27\">\u9ad8\u5ea6\u306a\u30b9\u30b3\u30fc\u30d7\u30c6\u30af\u30cb\u30c3\u30af<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class User &lt; ApplicationRecord\n  # NULL SAFE\u306a\u691c\u7d22\n  scope :by_email, -&gt;(email) {\n    return none if email.nil?\n    where(email: email)\n  }\n\n  # \u8907\u6570\u6761\u4ef6\u3067\u306e\u8907\u96d1\u306anil\u51e6\u7406\n  scope :with_complete_profile, -&gt; {\n    where.not(\n      name: nil,\n      email: nil\n    ).where.not(\n      profile: { bio: nil, avatar_url: nil }\n    ).joins(:profile)\n  }\nend<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-28\">\u95a2\u9023\u4ed8\u3051\u3067\u767a\u751f\u3059\u308bnil\u306e\u5bfe\u51e6\u6cd5<\/h3>\n\n\n\n<p>ActiveRecord\u306e\u95a2\u9023\u4ed8\u3051\u3067\u306f\u3001<code>nil<\/code>\u304c\u69d8\u3005\u306a\u5f62\u3067\u767a\u751f\u3059\u308b\u53ef\u80fd\u6027\u304c\u3042\u308a\u307e\u3059\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-29\">\u57fa\u672c\u7684\u306a\u95a2\u9023\u4ed8\u3051\u306enil\u5bfe\u7b56<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class Post &lt; ApplicationRecord\n  # \u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u3092\u6301\u3064\u95a2\u9023\u4ed8\u3051\n  belongs_to :category, -&gt; { with_deleted }, default: -&gt; { Category.default_category }\n\n  # \u30ab\u30b9\u30bf\u30e0\u30e1\u30bd\u30c3\u30c9\u3067nil\u5b89\u5168\u306a\u95a2\u9023\u4ed8\u3051\u30a2\u30af\u30bb\u30b9\n  def safe_author_name\n    author&amp;.name || 'Unknown Author'\n  end\n\n  # \u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u3067nil\u3092\u30c7\u30d5\u30a9\u30eb\u30c8\u5024\u306b\u7f6e\u304d\u63db\u3048\n  before_save :ensure_category_presence\n\n  private\n\n  def ensure_category_presence\n    self.category ||= Category.default_category\n  end\nend<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-30\">\u9ad8\u5ea6\u306a\u95a2\u9023\u4ed8\u3051\u51e6\u7406<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class Order &lt; ApplicationRecord\n  has_many :order_items\n  belongs_to :user\n\n  # \u95a2\u9023\u30c7\u30fc\u30bf\u3092\u542b\u3080\u30d0\u30ea\u30c7\u30fc\u30b7\u30e7\u30f3\n  validate :validate_items_presence\n\n  # nil\u304c\u767a\u751f\u3057\u306a\u3044\u3088\u3046\u306a\u30b9\u30b3\u30fc\u30d7\u4ed8\u304d\u306e\u95a2\u9023\n  has_many :valid_items, -&gt; { where.not(price: nil) }, \n           class_name: 'OrderItem'\n\n  # \u30ab\u30b9\u30bf\u30e0\u30e1\u30bd\u30c3\u30c9\u3067\u5b89\u5168\u306a\u96c6\u8a08\n  def total_price\n    order_items.sum { |item| item.price || 0 }\n  end\n\n  private\n\n  def validate_items_presence\n    if order_items.empty?\n      errors.add(:base, '\u6ce8\u6587\u9805\u76ee\u304c\u5fc5\u8981\u3067\u3059')\n    end\n  end\nend<\/pre>\n\n\n\n<p>\u3053\u308c\u3089\u306e\u30c6\u30af\u30cb\u30c3\u30af\u3092\u9069\u5207\u306b\u7d44\u307f\u5408\u308f\u305b\u308b\u3053\u3068\u3067\u3001\u30c7\u30fc\u30bf\u30d9\u30fc\u30b9\u64cd\u4f5c\u306b\u95a2\u9023\u3059\u308b<code>nil<\/code>\u306e\u554f\u984c\u3092\u52b9\u679c\u7684\u306b\u9632\u3050\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u8003\u616e\u3057\u305f<code>nil<\/code>\u51e6\u7406\u306e\u6700\u9069\u5316\u306b\u3064\u3044\u3066\u8aac\u660e\u3057\u3066\u3044\u304d\u307e\u3059\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-31\">\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u3092\u610f\u8b58\u3057\u305fnil\u51e6\u7406\u306e\u6700\u9069\u5316<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-32\">\u30e1\u30e2\u30ea\u52b9\u7387\u3092\u8003\u616e\u3057\u305fnil\u5224\u5b9a\u306e\u5b9f\u88c5<\/h3>\n\n\n\n<p>nil\u306e\u5224\u5b9a\u65b9\u6cd5\u306b\u3088\u3063\u3066\u3001\u30e1\u30e2\u30ea\u4f7f\u7528\u91cf\u3084\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306b\u9055\u3044\u304c\u751f\u3058\u307e\u3059\u3002\u4ee5\u4e0b\u3067\u306f\u3001\u52b9\u7387\u7684\u306anil\u5224\u5b9a\u306e\u5b9f\u88c5\u65b9\u6cd5\u3092\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-33\">\u30e1\u30e2\u30ea\u52b9\u7387\u306e\u826f\u3044nil\u5224\u5b9a\u30d1\u30bf\u30fc\u30f3<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class DataProcessor\n  # \u826f\u3044\u4f8b\uff1a\u76f4\u63a5\u7684\u306anil\u5224\u5b9a\n  def process_data(data)\n    return if data.nil?  # \u6700\u3082\u52b9\u7387\u7684\n    # \u51e6\u7406\u5185\u5bb9\n  end\n\n  # \u60aa\u3044\u4f8b\uff1a\u975e\u52b9\u7387\u306a\u5224\u5b9a\n  def process_data_inefficient(data)\n    return if data.to_s.empty?  # \u4f59\u5206\u306a\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u751f\u6210\u304c\u767a\u751f\n    # \u51e6\u7406\u5185\u5bb9\n  end\n\n  # \u30b3\u30ec\u30af\u30b7\u30e7\u30f3\u3067\u306e\u52b9\u7387\u7684\u306anil\u9664\u53bb\n  def clean_array(array)\n    array.compact  # \u65b0\u3057\u3044\u914d\u5217\u3092\u751f\u6210\n    # \u307e\u305f\u306f\n    array.compact!  # \u7834\u58ca\u7684\u30e1\u30bd\u30c3\u30c9\u3067\u30e1\u30e2\u30ea\u52b9\u7387\u6539\u5584\n  end\nend<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-34\">\u30ad\u30e3\u30c3\u30b7\u30e5\u3092\u6d3b\u7528\u3057\u305fnil\u5224\u5b9a\u306e\u6700\u9069\u5316<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class CachedProcessor\n  def initialize\n    @cache = {}\n  end\n\n  def process_with_cache(key)\n    # nil\u306e\u5834\u5408\u306e\u307f\u8a08\u7b97\u3092\u5b9f\u884c\n    @cache[key] ||= begin\n      expensive_calculation(key)\n    end\n  end\n\n  private\n\n  def expensive_calculation(key)\n    # \u91cd\u3044\u51e6\u7406\n  end\nend<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-35\">nil\u30ac\u30fc\u30c9\u7bc0\u306b\u3088\u308b\u51e6\u7406\u306e\u9ad8\u901f\u5316\u30c6\u30af\u30cb\u30c3\u30af<\/h3>\n\n\n\n<p>\u65e9\u671f\u30ea\u30bf\u30fc\u30f3\u3092\u6d3b\u7528\u3057\u305fnil\u51e6\u7406\u306f\u3001\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306e\u5411\u4e0a\u306b\u5bc4\u4e0e\u3057\u307e\u3059\uff1a<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-36\">\u52b9\u7387\u7684\u306a\u30ac\u30fc\u30c9\u7bc0\u30d1\u30bf\u30fc\u30f3<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class UserService\n  # \u826f\u3044\u4f8b\uff1a\u65e9\u671f\u30ea\u30bf\u30fc\u30f3\u3067\u4e0d\u8981\u306a\u51e6\u7406\u3092\u56de\u907f\n  def process_user(user)\n    return :invalid if user.nil?\n    return :unauthorized unless user.active?\n\n    perform_expensive_operation(user)\n  end\n\n  # \u914d\u5217\u51e6\u7406\u3067\u306e\u52b9\u7387\u7684\u306anil\u5bfe\u5fdc\n  def process_users(users)\n    return [] if users.nil?\n\n    users.each_with_object([]) do |user, result|\n      next if user.nil?  # nil\u306e\u8981\u7d20\u3092\u30b9\u30ad\u30c3\u30d7\n      result &lt;&lt; process_user(user)\n    end\n  end\n\n  private\n\n  def perform_expensive_operation(user)\n    # \u51e6\u7406\u5185\u5bb9\n  end\nend<\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-37\">\u30d0\u30c3\u30c1\u51e6\u7406\u3067\u306e\u6700\u9069\u5316<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class BatchProcessor\n  def process_batch(items)\n    # nil\u3092\u5148\u306b\u9664\u5916\u3057\u3066\u304b\u3089\u30d0\u30c3\u30c1\u51e6\u7406\n    valid_items = items.compact\n\n    valid_items.each_slice(100) do |batch|\n      process_slice(batch)\n    end\n  end\n\n  # \u30e1\u30e2\u30ea\u52b9\u7387\u3092\u8003\u616e\u3057\u305f\u30b9\u30c8\u30ea\u30fc\u30e0\u51e6\u7406\n  def stream_process(items)\n    items.lazy\n         .reject(&amp;:nil?)\n         .each_slice(100)\n         .each { |batch| process_slice(batch) }\n  end\n\n  private\n\n  def process_slice(batch)\n    # \u30d0\u30c3\u30c1\u51e6\u7406\u306e\u5185\u5bb9\n  end\nend<\/pre>\n\n\n\n<p>\u3053\u308c\u3089\u306e\u6700\u9069\u5316\u30c6\u30af\u30cb\u30c3\u30af\u3092\u9069\u7528\u3059\u308b\u3053\u3068\u3067\u3001nil\u51e6\u7406\u306b\u95a2\u9023\u3059\u308b\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u306e\u554f\u984c\u3092\u52b9\u679c\u7684\u306b\u89e3\u6c7a\u3067\u304d\u307e\u3059\u3002\u6b21\u306e\u30bb\u30af\u30b7\u30e7\u30f3\u3067\u306f\u3001\u3053\u308c\u307e\u3067\u306e\u77e5\u8b58\u3092\u6d3b\u304b\u3057\u305f\u5b9f\u8df5\u7684\u306a\u30b3\u30fc\u30c9\u4f8b\u3092\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"i-38\">\u5b9f\u8df5\u7684\u306a\u30b3\u30fc\u30c9\u4f8b\u3067\u5b66\u3076nil\u5bfe\u7b56\u30d1\u30bf\u30fc\u30f3<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-39\">\u30e6\u30fc\u30b6\u30fc\u60c5\u5831\u53d6\u5f97\u6642\u306enil\u5bfe\u7b56\u5b9f\u88c5\u4f8b<\/h3>\n\n\n\n<p>\u5b9f\u969b\u306eWeb\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3067\u3088\u304f\u906d\u9047\u3059\u308b\u3001\u30e6\u30fc\u30b6\u30fc\u60c5\u5831\u53d6\u5f97\u6642\u306enil\u5bfe\u7b56\u30d1\u30bf\u30fc\u30f3\u3092\u898b\u3066\u3044\u304d\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-40\">\u30e6\u30fc\u30b6\u30fc\u30d7\u30ed\u30d5\u30a3\u30fc\u30eb\u8868\u793a\u306e\u5b9f\u88c5<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class UserProfileService\n  class MissingUserError &lt; StandardError; end\n\n  def initialize(user_id)\n    @user_id = user_id\n  end\n\n  def display_info\n    user = find_user\n    {\n      name: user.name,\n      email: user.email,\n      profile: extract_profile_data(user.profile),\n      settings: extract_settings(user.settings)\n    }\n  rescue MissingUserError =&gt; e\n    handle_missing_user(e)\n  end\n\n  private\n\n  def find_user\n    User.find_by(id: @user_id) or raise MissingUserError\n  end\n\n  def extract_profile_data(profile)\n    return default_profile unless profile\n\n    {\n      bio: profile.bio || '\u30d7\u30ed\u30d5\u30a3\u30fc\u30eb\u306f\u307e\u3060\u4f5c\u6210\u3055\u308c\u3066\u3044\u307e\u305b\u3093',\n      avatar_url: profile.avatar_url || default_avatar_url,\n      location: profile.location || '\u672a\u8a2d\u5b9a'\n    }\n  end\n\n  def extract_settings(settings)\n    return default_settings if settings.nil?\n\n    settings.to_h.reverse_merge(default_settings)\n  end\n\n  def default_profile\n    {\n      bio: '\u30d7\u30ed\u30d5\u30a3\u30fc\u30eb\u306f\u307e\u3060\u4f5c\u6210\u3055\u308c\u3066\u3044\u307e\u305b\u3093',\n      avatar_url: default_avatar_url,\n      location: '\u672a\u8a2d\u5b9a'\n    }\n  end\n\n  def default_settings\n    {\n      notification: true,\n      theme: 'light',\n      language: 'ja'\n    }\n  end\n\n  def default_avatar_url\n    '\/images\/default_avatar.png'\n  end\n\n  def handle_missing_user(error)\n    Rails.logger.error \"User not found: #{error.message}\"\n    { error: '\u30e6\u30fc\u30b6\u30fc\u304c\u898b\u3064\u304b\u308a\u307e\u305b\u3093' }\n  end\nend<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-41\">API\u30ec\u30b9\u30dd\u30f3\u30b9\u51e6\u7406\u3067\u306enil\u5b89\u5168\u6027\u306e\u78ba\u4fdd<\/h3>\n\n\n\n<p>\u5916\u90e8API\u3068\u306e\u9023\u643a\u6642\u306b\u3088\u304f\u906d\u9047\u3059\u308b\u3001\u30ec\u30b9\u30dd\u30f3\u30b9\u51e6\u7406\u6642\u306enil\u5bfe\u7b56\u30d1\u30bf\u30fc\u30f3\u3067\u3059\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-42\">API\u30ec\u30b9\u30dd\u30f3\u30b9\u306e\u30d1\u30fc\u30b9\u51e6\u7406<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class ApiResponseHandler\n  def self.parse_response(response)\n    return { error: '\u30ec\u30b9\u30dd\u30f3\u30b9\u304c\u7a7a\u3067\u3059' } if response.nil?\n\n    begin\n      parsed = JSON.parse(response)\n      sanitize_response(parsed)\n    rescue JSON::ParserError =&gt; e\n      handle_parse_error(e)\n    end\n  end\n\n  def self.sanitize_response(data)\n    case data\n    when Hash\n      data.transform_values { |v| sanitize_response(v) }\n    when Array\n      data.map { |item| sanitize_response(item) }\n    when nil\n      nil\n    else\n      data\n    end\n  end\n\n  private\n\n  def self.handle_parse_error(error)\n    Rails.logger.error \"JSON parse error: #{error.message}\"\n    { error: '\u30ec\u30b9\u30dd\u30f3\u30b9\u306e\u89e3\u6790\u306b\u5931\u6557\u3057\u307e\u3057\u305f' }\n  end\nend\n\n# \u4f7f\u7528\u4f8b\nclass WeatherApiClient\n  def fetch_weather(city)\n    response = api_request(\"\/weather\/#{city}\")\n    data = ApiResponseHandler.parse_response(response)\n\n    {\n      temperature: data.dig('main', 'temp') || 'N\/A',\n      condition: data.dig('weather', 0, 'main') || '\u4e0d\u660e',\n      humidity: data.dig('main', 'humidity') || 'N\/A'\n    }\n  end\nend<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"i-43\">\u30d0\u30c3\u30c1\u51e6\u7406\u3067\u306e\u5805\u7262\u306anil\u51e6\u7406\u306e\u5b9f\u88c5<\/h3>\n\n\n\n<p>\u5927\u91cf\u306e\u30c7\u30fc\u30bf\u3092\u51e6\u7406\u3059\u308b\u30d0\u30c3\u30c1\u51e6\u7406\u3067\u306f\u3001nil\u306e\u6271\u3044\u304c\u7279\u306b\u91cd\u8981\u3067\u3059\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"i-44\">\u30c7\u30fc\u30bf\u79fb\u884c\u30d0\u30c3\u30c1\u306e\u5b9f\u88c5\u4f8b<\/h4>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">class DataMigrationService\n  class MigrationError &lt; StandardError; end\n\n  def initialize(source_data)\n    @source_data = source_data\n    @success_count = 0\n    @error_count = 0\n    @errors = []\n  end\n\n  def execute\n    return empty_result if @source_data.nil?\n\n    ActiveRecord::Base.transaction do\n      @source_data.each do |record|\n        process_record(record)\n      end\n\n      raise MigrationError if @error_count &gt; threshold\n\n      migration_result\n    end\n  rescue MigrationError =&gt; e\n    handle_migration_error(e)\n  end\n\n  private\n\n  def process_record(record)\n    return if record.nil?\n\n    begin\n      normalized_data = normalize_record(record)\n      save_record(normalized_data)\n      @success_count += 1\n    rescue StandardError =&gt; e\n      handle_record_error(record, e)\n      @error_count += 1\n    end\n  end\n\n  def normalize_record(record)\n    {\n      id: record['id'],\n      name: record['name']&amp;.strip,\n      email: record['email']&amp;.downcase,\n      status: record['status'] || 'pending',\n      metadata: record['metadata'].presence || {}\n    }.compact\n  end\n\n  def save_record(data)\n    TargetModel.create!(data)\n  end\n\n  def handle_record_error(record, error)\n    @errors &lt;&lt; {\n      record_id: record['id'],\n      error: error.message\n    }\n    Rails.logger.error \"Record processing failed: #{error.message}\"\n  end\n\n  def empty_result\n    {\n      status: :error,\n      message: '\u30bd\u30fc\u30b9\u30c7\u30fc\u30bf\u304c\u7a7a\u3067\u3059',\n      success_count: 0,\n      error_count: 0,\n      errors: []\n    }\n  end\n\n  def migration_result\n    {\n      status: :success,\n      message: '\u51e6\u7406\u304c\u5b8c\u4e86\u3057\u307e\u3057\u305f',\n      success_count: @success_count,\n      error_count: @error_count,\n      errors: @errors\n    }\n  end\n\n  def threshold\n    @source_data.size * 0.1 # 10%\u4ee5\u4e0a\u306e\u30a8\u30e9\u30fc\u3067\u5931\u6557\n  end\nend<\/pre>\n\n\n\n<p>\u3053\u308c\u3089\u306e\u5b9f\u88c5\u4f8b\u306f\u3001\u5b9f\u969b\u306e\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u3067\u3088\u304f\u906d\u9047\u3059\u308b\u72b6\u6cc1\u306b\u57fa\u3065\u3044\u3066\u3044\u307e\u3059\u3002\u30b3\u30fc\u30c9\u306e\u54c1\u8cea\u3092\u4fdd\u3061\u306a\u304c\u3089\u3001nil\u3092\u9069\u5207\u306b\u51e6\u7406\u3059\u308b\u3053\u3068\u3067\u3001\u3088\u308a\u5805\u7262\u306a\u30a2\u30d7\u30ea\u30b1\u30fc\u30b7\u30e7\u30f3\u3092\u69cb\u7bc9\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Warning: Undefined array key &#8220;is_admin&#8221; in 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<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":{"0":"post-1341","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-ruby","7":"nothumb"},"_links":{"self":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts\/1341","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1341"}],"version-history":[{"count":1,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts\/1341\/revisions"}],"predecessor-version":[{"id":1344,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=\/wp\/v2\/posts\/1341\/revisions\/1344"}],"wp:attachment":[{"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1341"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1341"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dexall.co.jp\/articles\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1341"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}