[{"data":1,"prerenderedAt":232},["ShallowReactive",2],{"article-in-rust-its-not-allow-to-modify-content-of-hashmap-while-iter-it":3},{"title":4,"article":5,"hot_article":18,"month_arch":81,"cover":229},"初学rust，不允许遍历过程中修改HashMap - 独孤影的博客",{"id":6,"title":7,"uri":8,"author":9,"tags":10,"created_at":15,"view_count":16,"content":17},115,"初学rust，不允许遍历过程中修改HashMap","in-rust-its-not-allow-to-modify-content-of-hashmap-while-iter-it","duguying",[11,12,13,14],"rust","HashMap","遍历","修改","2023-12-28 21:07:42",243,"\u003Cp>先看一段代码\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:#8b949e;font-weight:bold;font-style:italic\">#[\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">test\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\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">test_hash_map\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>mp: \u003Cspan style=\"color:#f0883e;font-weight:bold\">HashMap\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">str\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">str\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:#6e7681\"> \u003C\u002Fspan>HashMap::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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k1\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>x\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">=\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>mp.keys().clone();\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\">for\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>k\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">in\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>x\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k2\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k3\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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:#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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k2\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k3\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>看，它报错\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[E0502]: cannot borrow `mp` as mutable because it is also borrowed as immutable\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>   --> src\u002Fprocess.rs:153:9\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>    |\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>151 |     let x = mp.keys().clone();\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>    |             -- immutable borrow occurs here\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>152 |     for k in x {\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>    |              - immutable borrow later used here\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>153 |         mp.insert("k2", "v1");\n\u003C\u002Fspan>\u003C\u002Fspan>\u003Cspan style=\"display:flex;\">\u003Cspan>    |         ^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here\n\u003C\u002Fspan>\u003C\u002Fspan>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>报错告诉我们，不允许将\u003Ccode class=\"inline-code\">mp\u003C\u002Fcode>作为mutable，因为它已经用于immutable了。难道，HashMap插入数据完毕，开始读取数据之后，不能再次插入数据了？我一开始这么怀疑，不应该啊，于是代码改成这样\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:#8b949e;font-weight:bold;font-style:italic\">#[\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">test\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\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">test_hash_map\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>mp: \u003Cspan style=\"color:#f0883e;font-weight:bold\">HashMap\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">str\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">str\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:#6e7681\"> \u003C\u002Fspan>HashMap::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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k1\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>mp.keys().clone();\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k2\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k3\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>正常了，没报错了。看样子问题出在这个\u003Ccode class=\"inline-code\">for ..in..\u003C\u002Fcode>中。仔细分析代码，我在for中遍历了它的key，或者说我正在将这个HashMap中的数据拿出来，这时候，我在for中尝试往这个HashMap中写入数据，写入数据会让这个HashMap发生变更，这里第一感让我觉得可能有问题。比如我HashMap中有10个元素，我在遍历它，然后在for中间插入新元素，那么是不是有下列问题：1，我的HashMap会不会越遍历越多，会不会永远无法遍历完；2，HashMap是无序的，我将新元素插入HashMap中，会不会导致我已经遍历过的数据由于插入新数据，导致再次被读取出来，因为它可能位置发生变化了嘛。\u003C\u002Fp>\n\n\u003Cp>其实这就是数据竞争和它带来的不确定性问题，rust作为一个内存安全第一的编程语言，编译器会教你做人。\u003C\u002Fp>\n\n\u003Cp>于是，我再改\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:#8b949e;font-weight:bold;font-style:italic\">#[\u003C\u002Fspan>\u003Cspan style=\"color:#8b949e;font-weight:bold;font-style:italic\">test\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\">fn\u003C\u002Fspan> \u003Cspan style=\"color:#d2a8ff;font-weight:bold\">test_hash_map\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>mp: \u003Cspan style=\"color:#f0883e;font-weight:bold\">HashMap\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">str\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">str\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:#6e7681\"> \u003C\u002Fspan>HashMap::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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k1\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>x: Vec\u003Cspan style=\"color:#ff7b72;font-weight:bold\"><\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">&\u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">str\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:#6e7681\"> \u003C\u002Fspan>mp.keys().map(\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>k\u003Cspan style=\"color:#ff7b72;font-weight:bold\">|\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72;font-weight:bold\">*\u003C\u002Fspan>k).collect();\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\">for\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>k\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#ff7b72\">in\u003C\u002Fspan>\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>x\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k2\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k3\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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:#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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k2\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>mp.insert(\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">k3\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>,\u003Cspan style=\"color:#6e7681\"> \u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">"\u003C\u002Fspan>\u003Cspan style=\"color:#a5d6ff\">v1\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>\u003C\u002Fcode>\u003C\u002Fpre>\n\n\u003Cp>这回正常了。可以看到我的操作\u003Ccode class=\"inline-code\">let x: Vec<&str> = mp.keys().map(|k| *k).collect();\u003C\u002Fcode>是将keys()拿到的\u003Ccode class=\"inline-code\">Keys\u003C\u002Fcode>迭代器（仍旧从前面的HashMap里迭代）通过\u003Ccode class=\"inline-code\">.collect()\u003C\u002Fcode>方法将迭代器里的元素“倒”入到\u003Ccode class=\"inline-code\">Vec<&str>\u003C\u002Fcode>，这样这个\u003Ccode class=\"inline-code\">Vec\u003C\u002Fcode>就是一个独立与HashMap内存空间之外的变量，再基于这个Vec进行遍历，就可以避免“边遍历边修改的”的情况了。\u003C\u002Fp>\n\n\u003Cp>那么大家可以思考一下，其他语言，比如golang，遇到这种情况是怎么处理的呢。\u003C\u002Fp>\n",{"title":19,"list":20},"最热文章",[21,27,33,39,45,51,57,63,69,75],{"id":22,"title":23,"uri":24,"author":9,"created_at":25,"view_count":26},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":28,"title":29,"uri":30,"author":9,"created_at":31,"view_count":32},21,"beego中使用fis","\u002Farticle\u002Fbeego中使用fis","2014-12-03 10:47:56",9253,{"id":34,"title":35,"uri":36,"author":9,"created_at":37,"view_count":38},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":40,"title":41,"uri":42,"author":9,"created_at":43,"view_count":44},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":46,"title":47,"uri":48,"author":9,"created_at":49,"view_count":50},49,"用latex排版中文书籍","\u002Farticle\u002F用latex排版中文书籍","2016-10-31 11:12:02",8645,{"id":52,"title":53,"uri":54,"author":9,"created_at":55,"view_count":56},19,"texlive中文书签乱码","\u002Farticle\u002Ftexlive中文书签乱码","2014-11-15 02:54:01",8466,{"id":58,"title":59,"uri":60,"author":9,"created_at":61,"view_count":62},6,"Windows上的软件包管理器chocolatey","\u002Farticle\u002FWindows上的软件包管理器chocolatey","2014-08-10 15:55:22",8012,{"id":64,"title":65,"uri":66,"author":9,"created_at":67,"view_count":68},3,"利用开源和免费资源搭建CI环境","\u002Farticle\u002F利用开源和免费资源搭建CI环境","2014-07-04 16:54:58",7740,{"id":70,"title":71,"uri":72,"author":9,"created_at":73,"view_count":74},16,"php-fpm网站目录权限配置","\u002Farticle\u002Fphp-fpm网站目录权限配置","2014-10-18 01:36:10",7276,{"id":76,"title":77,"uri":78,"author":9,"created_at":79,"view_count":80},27,"sublime text 2插件开发，外部修改文件无法重新加载","\u002Farticle\u002Fsublime text 2插件开发，外部修改文件无法重新加载","2014-12-26 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