{"id":207247,"date":"2025-07-08T10:39:12","date_gmt":"2025-07-08T02:39:12","guid":{"rendered":"https:\/\/server.hk\/cnblog\/207247\/"},"modified":"2025-07-08T10:39:12","modified_gmt":"2025-07-08T02:39:12","slug":"%e6%98%af%e5%90%a6%e5%8f%af%e4%bb%a5%e6%8d%95%e8%8e%b7%e8%bf%99%e4%b8%aa-nil-%e6%8c%87%e9%92%88%e9%94%99%e8%af%af","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/207247\/","title":{"rendered":"\u662f\u5426\u53ef\u4ee5\u6355\u83b7\u8fd9\u4e2a nil \u6307\u9488\u9519\u8bef"},"content":{"rendered":"

<\/b> <\/p>\n

\u5f53\u524d\u4f4d\u7f6e\uff1a ><\/span> ><\/span> ><\/span> ><\/span> \u662f\u5426\u53ef\u4ee5\u6355\u83b7\u8fd9\u4e2a nil \u6307\u9488\u9519\u8bef<\/span><\/p>\n

\u6765\u6e90\uff1astackoverflow<\/span>
\n2024-04-21 08:45:33<\/span>
\n<\/i>0\u6d4f\u89c8<\/span>
\n<\/i>\u6536\u85cf<\/span> <\/p>\n

\u79ef\u7d2f\u77e5\u8bc6\uff0c\u80dc\u8fc7\u79ef\u84c4\u91d1\u94f6\uff01\u6bd5\u7adf\u5728Golang\u5f00\u53d1\u7684\u8fc7\u7a0b\u4e2d\uff0c\u4f1a\u9047\u5230\u5404\u79cd\u5404\u6837\u7684\u95ee\u9898\uff0c\u5f80\u5f80\u90fd\u662f\u4e00\u4e9b\u7ec6\u8282\u77e5\u8bc6\u70b9\u8fd8\u6ca1\u6709\u638c\u63e1\u597d\u800c\u5bfc\u81f4\u7684\uff0c\u56e0\u6b64\u57fa\u7840\u77e5\u8bc6\u70b9\u7684\u79ef\u7d2f\u662f\u5f88\u91cd\u8981\u7684\u3002\u4e0b\u9762\u672c\u6587\u300a\u662f\u5426\u53ef\u4ee5\u6355\u83b7\u8fd9\u4e2a nil \u6307\u9488\u9519\u8bef\u300b\uff0c\u5c31\u5e26\u5927\u5bb6\u8bb2\u89e3\u4e00\u4e0b\u77e5\u8bc6\u70b9\uff0c\u82e5\u662f\u4f60\u5bf9\u672c\u6587\u611f\u5174\u8da3\uff0c\u6216\u8005\u662f\u60f3\u641e\u61c2\u5176\u4e2d\u67d0\u4e2a\u77e5\u8bc6\u70b9\uff0c\u5c31\u8bf7\u4f60\u7ee7\u7eed\u5f80\u4e0b\u770b\u5427~<\/p>\n

\u95ee\u9898\u5185\u5bb9
\n <\/p>\n

\u6211\u6709\u4e00\u4e2a\u7f16\u8bd1\u5668\u65e0\u6cd5\u53d1\u73b0\u7684\u201cnil \u6307\u9488\u201d\u9519\u8bef\uff0c\u4f46\u6211\u60f3\u770b\u770b\u662f\u5426\u6709\u529e\u6cd5\u901a\u8fc7\u9759\u6001\u5206\u6790\u6765\u627e\u5230\u5b83\u3002 <\/p>\n

\u6240\u4ee5\u8fd9\u4e2abug\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n

package main\n\nimport (\n    \"fmt\"\n)\n\ntype a struct {\n    name string\n}\n\nfunc newgooda() (*a, error) {\n    return &a{\n        name: \"go\",\n    }, nil\n}\n\nfunc newbada() (*a, error) {\n    return nil, fmt.errorf(\"failed to create a\")\n}\n\nfunc (a *a) greet() string {\n    return \"hello \" + a.name\n}\n\nfunc main() {\n    valuea, err := newbada()\n    if err != nil {\n        fmt.printf(\"oops, failed because: %v\", valuea.greet()) \/\/ this should be forbidden, because when err is not nil, valuea shouldn't be touched\n    }\n}<\/pre>\n
\u5f53\u6211\u8fd0\u884c\u5b83\u65f6\uff0c\u51fa\u73b0\u9519\u8bef\uff0c\u56e0\u4e3a valuea<\/code> \u662f nil<\/code>\u3002<\/p>\n
panic: runtime error: invalid memory address or nil pointer dereference<\/pre>\n
\u8fd9\u662f\u4e00\u4e2a\u5e38\u89c1\u7684\u9519\u8bef\uff0c\u4f46\u7f16\u8bd1\u5668\u65e0\u6cd5\u53d1\u73b0\u3002\u6211\u60f3\u77e5\u9053\u662f\u5426\u6709\u4efb\u4f55\u5de5\u5177\u53ef\u4ee5\u9759\u6001\u5206\u6790\u4ee3\u7801\u5e76\u627e\u51fa\u8fd9\u4e00\u70b9\u3002<\/p>\n
\u5982\u679c\u89c4\u5219\u662f\u8fd9\u6837\u7684\u8bdd\uff0c\u6211\u89c9\u5f97\u8fd9\u662f\u53ef\u80fd\u7684\uff1a<\/p>\n
\u5982\u679c\u51fd\u6570\u8c03\u7528\u8fd4\u56de\u4e00\u4e2a\u503c\u548c\u4e00\u4e2a\u9519\u8bef\uff0c\u5219 if err != nil<\/code> \u903b\u8f91\u4e0d\u5e94\u89e6\u53ca\u8be5\u8fd4\u56de\u503c\uff08\u672c\u4f8b\u4e2d\u4e3a valuea<\/code>\uff09\uff0c\u56e0\u4e3a\u8fd9\u5f88\u5371\u9669\uff0c\u800c\u4e14\u5f88\u53ef\u80fd\u662f nil<\/code>\u3002<\/p>\n
\u6709\u4ec0\u4e48\u5de5\u5177\u53ef\u4ee5\u505a\u5230\u8fd9\u4e00\u70b9\u5417\uff1f<\/p>\n
 <\/p>\n
\u89e3\u51b3\u65b9\u6848<\/h2>\n
 <\/p>\n
\u5728 newbada \u8fd4\u56de\u9519\u8bef\u7684\u60c5\u51b5\u4e0b\uff0c\u5373\u4f7f valuea \u4e3a nil\uff0c\u4e5f\u4e0d\u80fd\u4f7f\u7528 valuea\uff0c\u8fd9\u79cd\u8bf4\u6cd5\u662f\u4e0d\u6b63\u786e\u7684\u3002 go \u4f1a\u5f88\u4e50\u610f\u5728 nil \u63a5\u6536\u5668\u4e0a\u8c03\u7528\u8be5\u51fd\u6570 – \u4f8b\u5982\uff1a<\/p>\n
func (a *A) greet() string {\n   if a == nil {\n      return \"(nil)\"\n   }\n   return a.name\n}<\/pre>\n
\u4eca\u5929\u5173\u4e8e\u300a\u662f\u5426\u53ef\u4ee5\u6355\u83b7\u8fd9\u4e2a nil \u6307\u9488\u9519\u8bef\u300b\u7684\u5185\u5bb9\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\uff0c\u5982\u679c\u6709\u4ec0\u4e48\u7591\u95ee\u6216\u8005\u5efa\u8bae\uff0c\u53ef\u4ee5\u5728\u516c\u4f17\u53f7\u4e0b\u591a\u591a\u56de\u590d\u4ea4\u6d41\uff1b\u6587\u4e2d\u82e5\u6709\u4e0d\u6b63\u4e4b\u5904\uff0c\u4e5f\u5e0c\u671b\u56de\u590d\u7559\u8a00\u4ee5\u544a\u77e5\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5f53\u524d\u4f4d\u7f6e\uff1a > > ...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4925],"tags":[],"class_list":["post-207247","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/207247","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=207247"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/207247\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=207247"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=207247"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=207247"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}