[{"data":1,"prerenderedAt":240},["ShallowReactive",2],{"tag-rust-3":3},{"title":4,"articles":5,"hot_article":25,"month_arch":88,"total":236,"cover":237},"rust 第3页 - 独孤影的博客",[6,17],{"id":7,"title":8,"uri":9,"author":10,"tags":11,"created_at":14,"view_count":15,"content":16},74,"初学rust，闭包引用外部变量","closure-can-not-use-var-outsite-the-closure-function","duguying",[12,13],"rust","闭包","2022-09-27 22:44:09",408,"\u003Cp>今天又遇到一个新的问题，那就是在闭包函数中，无法引用闭包函数之外的变量。\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">main\u003C\u002Fspan>()\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>cfg\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>config::cfg::get_config();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>filename\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>cfg.las.as_ref().unwrap().access_log.as_ref().unwrap();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u002F\u002F println!("{}",filename);\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u002F\u002F let mut p = poly::Poly::new();\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>s\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>String::from(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">_\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>);\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>log_watcher\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>LogWatcher::register(filename.to_string()).unwrap();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>log_watcher.watch(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>line: String\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>(_,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>token)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>parse::lex::parser(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>line);\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u002F\u002F p.push(LineStat {});\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>print!\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>(\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">{}\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>s);\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>process::report::send(token);\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>});\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>上面代码中，\u003Ccode class=\"inline-code\">watch\u003C\u002Fcode>传入参数为一个闭包函数，其中需要引用\u003Ccode class=\"inline-code\">main\u003C\u002Fcode>函数中的局部变量\u003Ccode class=\"inline-code\">s\u003C\u002Fcode>，但是会报错\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>error[E0308]: mismatched types\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>  --> src\u002Fmain.rs:22:23\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   |\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>22 |       log_watcher.watch(|line: String| {\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   |  _______________________^\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>23 | |         let (_, token) = parse::lex::parser(&line);\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>24 | |         \u002F\u002F p.push(LineStat {});\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>25 | |         print!("{}", s);\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>26 | |         process::report::send(token);\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>27 | |     });\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   | |_____^ expected fn pointer, found closure\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   |\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   = note: expected fn pointer `fn(std::string::String)`\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>                 found closure `[closure@src\u002Fmain.rs:22:23: 27:6]`\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>note: closures can only be coerced to `fn` types if they do not capture any variables\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>查看\u003Ccode class=\"inline-code\">logwatcher\u003C\u002Fcode>源码，\u003Ccode class=\"inline-code\">watch\u003C\u002Fcode>该版本(0.1.0)方法定义如下\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#ff7b72\">pub\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">watch\u003C\u002Fspan>(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>self,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>callback: \u003Cspan style=\"color:#f0883e;font-weight:bold\">fn\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>(line: String))\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">..\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">..\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>不过我后来发现\u003Ccode class=\"inline-code\">logwatcher\u003C\u002Fcode>版本升级到(0.1.1)之后，该方法变为\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#ff7b72\">pub\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">watch\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>F: \u003Cspan style=\"color:#ff7b72;font-weight:bold\">?\u003C\u002Fspan>Sized\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>self,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>callback: \u003Cspan style=\"color:#79c0ff\">&\u003C\u002Fspan>\u003Cspan style=\"color:#f0883e;font-weight:bold\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>F)\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">where\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>F: FnMut(String)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>-> \u003Cspan style=\"color:#f0883e;font-weight:bold\">LogWatcherAction\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">..\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">..\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>如此可以正常调用，代码如下\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">main\u003C\u002Fspan>()\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>cfg\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>config::cfg::get_config();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>filename\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>cfg.las.as_ref().unwrap().access_log.as_ref().unwrap();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>watcher\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>LogWatcher::register(filename.to_string()).unwrap();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>poly: \u003Cspan style=\"color:#f0883e;font-weight:bold\">Poly\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>Poly::new();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>watcher.watch(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>line: String\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>poly.clone().push(line);\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>LogWatcherAction::None\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>})\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>由此可见，闭包与函数还是有区别的。但是回调函数定义为Fn\u002FFnMut类型就可以同时接受闭包和函数类型的回调参数。举例如下\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>a\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>String::from(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">abc\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>);\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>x\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>println!\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>(\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">x \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">{}\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>a);\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">y\u003C\u002Fspan>()\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>println!\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>(\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">y\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>)\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">wrap\u003C\u002Fspan>(c: \u003Cspan style=\"color:#79c0ff\">&\u003C\u002Fspan>\u003Cspan style=\"color:#f0883e;font-weight:bold\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>Fn())\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>c()\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>wrap(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>x);\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u002F\u002F pass a closure\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u003C\u002Fspan>wrap(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>y);\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-style:italic\">\u002F\u002F pass a function\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>同样可以参考 \u003Cstrong>stackoverflow\u003C\u002Fstrong> 的这个\u003Ca href=\"https:\u002F\u002Fstackoverflow.com\u002Fquestions\u002F52696907\u002Fwhy-does-passing-a-closure-to-function-which-accepts-a-function-pointer-not-work\">提问\u003C\u002Fa>。\u003C\u002Fp>\n",{"id":18,"title":19,"uri":20,"author":10,"tags":21,"created_at":22,"view_count":23,"content":24},67,"初学rust，为什么对象不能被函数返回","think-of-rust-beginning-learner-why-can-not-return-an-object",[12],"2022-08-24 10:50:06",384,"\u003Cp>7年前，我选择了自学golang，事实证明我选择对了。目前业界用golang的人越来越多，也越来越卷。于是我就想选择另一门语言了。用了这些年的golang之后，感觉golang在很多场景下还是很难胜任高新能开发；另外，我特别羡慕能做底层开发的同学，比如内核开发、协议栈开发等；因此，我看上了rust，rust号称无gc，甚至还能开发linux内核，还有一些游戏引擎，数据库引擎也是用rust开发的，一听就特别高端是吧。\u003C\u002Fp>\n\n\u003Cp>于是我作为一个新手，开始尝试上手rust，原本准备依照golang的学习路线，先写个博客或者小的web程序，但是，发现rust上手太难。于是降低了上手的要求，用rust重写了一遍我的pinyin项目，项目是将汉字翻译成拼音，支持多音词，需要接入字词库。折腾了许久，终于完成了；这里简单谈一下作为一个rust初学者的感受。\u003C\u002Fp>\n\n\u003Cp>\u003Cimg src=\"https:\u002F\u002Fimage.duguying.net\u002F2022\u002F08\u002Fxtyiguc3.webp\" alt=\"xtyiguc3\" \u002F>\u003C\u002Fp>\n\n\u003Cp>首先，最大一个问题就是局部变量无法在作用域之外使用，这在golang上会自动扩大作用域，无需考虑这些问题。比如，我在一个函数中创建出来的对象，return返回后，发现无法在外部访问，直接报错，实际上该对象在函数结束时已经被销毁。或者说，所在对象发生move，因为他的类型未实现Copy trait。\u003C\u002Fp>\n\n\u003Cp>\u003Cimg src=\"https:\u002F\u002Fimage.duguying.net\u002F2022\u002F09\u002F79dsu2ub.png\" alt=\"79dsu2ub\" \u002F>\u003C\u002Fp>\n\n\u003Cp>比如，这种报错经常发生在这么一个场景，我创建了一个config包，辛苦的在里面实现了加载配置文件到一个结构体，当我完成这些之后，希望在另一个mod中引用这个config结构体，便会经常发生这种情况。\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#ff7b72\">use\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>std::fs::File;\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">use\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>std::io::prelude::\u003Cspan style=\"color:#ff7b72;font-weight:bold\">*\u003C\u002Fspan>;\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">use\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>once_cell::sync::Lazy;\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">#[\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">derive(Deserialize)\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">]\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">#[\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">derive(Debug)\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">]\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">struct\u003C\u002Fspan> \u003Cspan style=\"color:#f0883e;font-weight:bold\">LasConfig\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">pub\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>access_log: Option\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>String\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">#[\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">derive(Deserialize)\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">]\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">#[\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">derive(Debug)\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">]\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">struct\u003C\u002Fspan> \u003Cspan style=\"color:#f0883e;font-weight:bold\">Conf\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">pub\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>las: Option\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>LasConfig\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">static\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>global: \u003Cspan style=\"color:#f0883e;font-weight:bold\">Lazy\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>Conf\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>Lazy::new(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>file_path\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">config.toml\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>;\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>file\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">match\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>File::open(file_path)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>Ok(f)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>f,\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>Err(e)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>panic!\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>(\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">no such file \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">{}\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\"> exception:\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">{}\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>file_path,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>e)\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>};\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">let\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>str_val\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>String::new();\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">match\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>file.read_to_string(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">mut\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>str_val)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>Ok(s)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>s,\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">        \u003C\u002Fspan>Err(e)\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">>\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>panic!\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>(\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">Error Reading file: \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">{}\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>e)\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>};\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>toml::from_str(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>str_val).unwrap()\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>});\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">pub\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">get_config\u003C\u002Fspan>()\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>-> \u003Cspan style=\"color:#f0883e;font-weight:bold\">Conf\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">    \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">*\u003C\u002Fspan>global\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>其中\u003Ccode class=\"inline-code\">*global\u003C\u002Fcode>的类型的确是\u003Ccode class=\"inline-code\">Conf\u003C\u002Fcode>但是却无法通过参数返回。会有如下的报错信息\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>error[E0507]: cannot move out of dereference of `once_cell::sync::Lazy<Conf>`\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>  --> src\u002Fconfig\u002Fcfg.rs:32:5\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   |\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>32 |     *global\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   |     ^^^^^^^ move occurs because value has type `Conf`, which does not implement the `Copy` trait\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>For more information about this error, try `rustc --explain E0507`.\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>\u003Cimg src=\"https:\u002F\u002Fimage.duguying.net\u002F2022\u002F09\u002Fe463qi5x.png\" alt=\"e463qi5x\" \u002F>\u003C\u002Fp>\n\n\u003Cp>很明显，这里生成的\u003Ccode class=\"inline-code\">Conf\u003C\u002Fcode>类型的\u003Ccode class=\"inline-code\">global\u003C\u002Fcode>对象，但是无法直接返回。因为返回的时候发生了\u003Ccode class=\"inline-code\">move\u003C\u002Fcode>。\u003C\u002Fp>\n\n\u003Cp>神奇的是，这里\u003Ccode class=\"inline-code\">get_config()\u003C\u002Fcode>改成如下这样，就不会有报错了\u003C\u002Fp>\n\n\u003Cpre style=\"color:#e6edf3;background-color:#0d1117;white-space:pre-wrap;word-break:break-word;\">\u003Ccode>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#ff7b72\">pub\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">get_config\u003C\u002Fspan>()\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>-> \u003Cspan style=\"color:#79c0ff\">&\u003C\u002Fspan>'static \u003Cspan style=\"color:#f0883e;font-weight:bold\">Conf\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>{\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\">   \u003C\u002Fspan>(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">*\u003C\u002Fspan>global).borrow()\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>\u003Cspan style=\"color:#6e7681\">\u003C\u002Fspan>}\u003Cspan style=\"color:#6e7681\">\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>我们从\u003Ca href=\"https:\u002F\u002Fdoc.rust-lang.org\u002Ferror-index.html#E0507\">E0507\u003C\u002Fa>这篇文章中可以看到\u003C\u002Fp>\n\n\u003Cblockquote>\n\u003Cp>the \u003Ccode class=\"inline-code\">nothing_is_true method\u003C\u002Fcode> takes the ownership of \u003Ccode class=\"inline-code\">self\u003C\u002Fcode>\u003C\u002Fp>\n\u003C\u002Fblockquote>\n\n\u003Cp>那么我们这里的报错应该也是\u003Ccode class=\"inline-code\">*global\u003C\u002Fcode>在返回的时候，将ownership拿走，既然不能拿走，那就改为借用好了。\u003C\u002Fp>\n",{"title":26,"list":27},"最热文章",[28,34,40,46,52,58,64,70,76,82],{"id":29,"title":30,"uri":31,"author":10,"created_at":32,"view_count":33},28,"docker容器目录与主机目录同步","\u002Farticle\u002Fdocker容器目录与主机目录同步","2014-12-31 12:34:08",15573,{"id":35,"title":36,"uri":37,"author":10,"created_at":38,"view_count":39},21,"beego中使用fis","\u002Farticle\u002Fbeego中使用fis","2014-12-03 10:47:56",9253,{"id":41,"title":42,"uri":43,"author":10,"created_at":44,"view_count":45},20,"用github登录，oauth开发","\u002Farticle\u002F用github登录，oauth开发","2014-11-23 13:33:37",9115,{"id":47,"title":48,"uri":49,"author":10,"created_at":50,"view_count":51},18,"windows服务注册工具nssm","\u002Farticle\u002Fwindows服务注册工具nssm","2014-10-31 21:34:39",9054,{"id":53,"title":54,"uri":55,"author":10,"created_at":56,"view_count":57},49,"用latex排版中文书籍","\u002Farticle\u002F用latex排版中文书籍","2016-10-31 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