{"id":2338,"date":"2025-09-19T11:36:45","date_gmt":"2025-09-19T03:36:45","guid":{"rendered":"https:\/\/www.madbull.site\/?p=2338"},"modified":"2025-09-19T15:33:48","modified_gmt":"2025-09-19T07:33:48","slug":"lua-%e4%b8%ad%e7%9a%84-__index%e3%80%81__newindex%e3%80%81rawget-%e4%b8%8e-rawset-%e4%bb%8b%e7%bb%8d","status":"publish","type":"post","link":"https:\/\/www.madbull.site\/?p=2338","title":{"rendered":"Lua \u4e2d\u7684 __index\u3001__newindex\u3001rawget \u4e0e rawset \u4ecb\u7ecd"},"content":{"rendered":"\n

\u5728 Lua \u4e2d\uff0c\u8868\uff08table\uff09\u662f\u6700\u6838\u5fc3\u7684\u6570\u636e\u7ed3\u6784\u3002\u901a\u8fc7\u4e3a\u5176\u8bbe\u7f6e\u201c\u5143\u8868\u201d\uff08metatable\uff09\uff0c\u6211\u4eec\u53ef\u4ee5\u6539\u53d8\u8868\u5728\u67d0\u4e9b\u64cd\u4f5c\u4e0b\u7684\u9ed8\u8ba4\u884c\u4e3a\u3002\u5176\u4e2d\uff0c__index<\/code> \u548c __newindex<\/code> \u662f\u4e24\u4e2a\u6700\u5e38\u7528\u7684\u5143\u65b9\u6cd5\uff0c\u800c rawget<\/code> \u548c rawset<\/code> \u662f\u4e0e\u4e4b\u914d\u5957\u7684\u201c\u7ed5\u8fc7\u5143\u8868\u201d\u7684\u64cd\u4f5c\u51fd\u6570\u3002\u7406\u89e3\u5b83\u4eec\u7684\u4f5c\u7528\u548c\u5173\u7cfb\uff0c\u6709\u52a9\u4e8e\u66f4\u7075\u6d3b\u3001\u5b89\u5168\u5730\u4f7f\u7528 Lua \u8868\u3002<\/p>\n\n\n\n

\n\n\n\n

\u4e00\u3001__index<\/code> \u2014\u2014 \u8bfb\u53d6\u4e0d\u5b58\u5728\u7684\u952e\u65f6\u7684\u884c\u4e3a<\/h2>\n\n\n\n

\u5f53\u8bbf\u95ee\u4e00\u4e2a\u8868\u4e2d\u4e0d\u5b58\u5728\u7684\u952e\u65f6\uff08\u4f8b\u5982 t.key<\/code> \u6216 t[\"key\"]<\/code>\uff09\uff0c\u5982\u679c\u8be5\u8868\u8bbe\u7f6e\u4e86\u5143\u8868\uff0c\u4e14\u5143\u8868\u4e2d\u5305\u542b __index<\/code> \u5b57\u6bb5\uff0cLua \u5c31\u4f1a\u8c03\u7528\u5b83\u3002<\/p>\n\n\n\n

__index<\/code> \u53ef\u4ee5\u662f\u4e00\u4e2a\u51fd\u6570<\/strong>\uff0c\u4e5f\u53ef\u4ee5\u662f\u4e00\u4e2a\u8868<\/strong>\u3002<\/p>\n\n\n\n

\u793a\u4f8b 1\uff1a__index<\/code> \u662f\u51fd\u6570<\/h3>\n\n\n\n
local<\/strong> t = {}\nlocal<\/strong> mt = {\n    __index = function<\/strong>(tbl, key)\n        print(\"\u8bbf\u95ee\u4e86\u4e0d\u5b58\u5728\u7684\u952e:\", key)\n        return<\/strong> nil<\/strong>\n    end<\/strong>\n}\nsetmetatable(t, mt)\n\nprint(t.name)  -- \u8f93\u51fa: \u8bbf\u95ee\u4e86\u4e0d\u5b58\u5728\u7684\u952e: name\n               -- \u7136\u540e\u8f93\u51fa: nil<\/code><\/pre>\n\n\n\n
\u793a\u4f8b 2\uff1a__index<\/code> \u662f\u8868\uff08\u5e38\u7528\u4e8e\u201c\u9ed8\u8ba4\u503c\u201d\u6216\u201c\u7ee7\u627f\u201d\uff09<\/h3>\n\n\n\n
local<\/strong> defaults = { x = 0, y = 0 }\nlocal<\/strong> obj = {}\nsetmetatable(obj, { __index = defaults })\n\nprint(obj.x)  -- 0\uff08\u4ece defaults \u83b7\u53d6\uff09\nprint(obj.z)  -- nil\uff08defaults \u91cc\u4e5f\u6ca1\u6709\uff09<\/code><\/pre>\n\n\n\n
\n
\u6ce8\u610f\uff1a\u5982\u679c\u952e\u5728\u8868\u4e2d\u5df2\u5b58\u5728\uff0c\u5219\u4e0d\u4f1a\u89e6\u53d1 __index<\/code>\u3002<\/p>\n<\/blockquote>\n\n\n\n
\n\n\n\n
\u4e8c\u3001__newindex<\/code> \u2014\u2014 \u5199\u5165\u4e0d\u5b58\u5728\u7684\u952e\u65f6\u7684\u884c\u4e3a<\/h2>\n\n\n\n
\u5f53\u7ed9\u4e00\u4e2a\u8868\u4e2d\u539f\u672c\u4e0d\u5b58\u5728\u7684\u952e<\/strong>\u8d4b\u503c\u65f6\uff08\u4f8b\u5982 t.key = value<\/code>\uff09\uff0c\u5982\u679c\u8be5\u8868\u6709\u5143\u8868\u4e14\u5b9a\u4e49\u4e86 __newindex<\/code>\uff0cLua \u4f1a\u8c03\u7528\u5b83\uff0c\u800c\u4e0d\u662f\u76f4\u63a5\u8d4b\u503c\u3002<\/p>\n\n\n\n
\u548c __index<\/code> \u4e00\u6837\uff0c__newindex<\/code> \u4e5f\u53ef\u4ee5\u662f\u51fd\u6570\u6216\u8868\u3002<\/p>\n\n\n\n
\u793a\u4f8b 1\uff1a__newindex<\/code> \u662f\u51fd\u6570\uff08\u5e38\u7528\u4e8e\u62e6\u622a\u3001\u6821\u9a8c\u3001\u65e5\u5fd7\uff09<\/h3>\n\n\n\n
local<\/strong> t = {}\nlocal<\/strong> mt = {\n    __newindex = function<\/strong>(tbl, key, value)\n        print(\"\u5c1d\u8bd5\u8bbe\u7f6e:\", key, \"=\", value)\n        -- \u53ef\u9009\u62e9\u662f\u5426\u771f\u6b63\u5199\u5165\n        rawset(tbl, key, value)  -- \u4f7f\u7528 rawset \u907f\u514d\u9012\u5f52\n    end<\/strong>\n}\nsetmetatable(t, mt)\n\nt.name = \"Alice\"  -- \u8f93\u51fa: \u5c1d\u8bd5\u8bbe\u7f6e: name = Alice\nprint(t.name)     -- Alice<\/code><\/pre>\n\n\n\n
\u793a\u4f8b 2\uff1a__newindex<\/code> \u662f\u8868\uff08\u5e38\u7528\u4e8e\u201c\u5199\u5165\u91cd\u5b9a\u5411\u201d\uff09<\/h3>\n\n\n\n
local<\/strong> storage = {}\nlocal<\/strong> proxy = {}\nsetmetatable(proxy, { __newindex = storage })\n\nproxy.x = 10\nproxy.y = 20\n\nprint(proxy.x, proxy.y)     -- nil, nil\uff08proxy \u672c\u8eab\u6ca1\u5199\u5165\uff09\nprint(storage.x, storage.y) -- 10, 20\uff08\u5199\u5165\u5230\u4e86 storage\uff09<\/code><\/pre>\n\n\n\n
\n
\u6ce8\u610f\uff1a<\/p>\n\n\n\n
    \n
  • \u5982\u679c\u952e\u5df2\u5b58\u5728\uff0c\u8d4b\u503c\u4e0d\u4f1a\u89e6\u53d1 __newindex<\/code>\u3002<\/li>\n\n\n\n
  • \u5728 __newindex<\/code> \u51fd\u6570\u5185\u76f4\u63a5\u5199 tbl[key] = value<\/code> \u4f1a\u5bfc\u81f4\u65e0\u9650\u9012\u5f52\uff0c\u5e94\u4f7f\u7528 rawset<\/code>\u3002<\/li>\n<\/ul>\n<\/blockquote>\n\n\n\n
    \n\n\n\n
    \u4e09\u3001rawget<\/code> \u4e0e rawset<\/code> \u2014\u2014 \u7ed5\u8fc7\u5143\u8868\u7684\u76f4\u63a5\u64cd\u4f5c<\/h2>\n\n\n\n
    \u6709\u65f6\u6211\u4eec\u5e0c\u671b\u8df3\u8fc7\u5143\u8868\u673a\u5236<\/strong>\uff0c\u76f4\u63a5\u5bf9\u8868\u8fdb\u884c\u8bfb\u5199\u3002\u8fd9\u65f6\u5c31\u9700\u8981 rawget<\/code> \u548c rawset<\/code>\u3002<\/p>\n\n\n\n
      \n
    • rawget(t, key)<\/code> \u2192 \u76f4\u63a5\u83b7\u53d6 t[key]<\/code>\uff0c\u4e0d\u89e6\u53d1 __index<\/code><\/li>\n\n\n\n
    • rawset(t, key, value)<\/code> \u2192 \u76f4\u63a5\u8bbe\u7f6e t[key] = value<\/code>\uff0c\u4e0d\u89e6\u53d1 __newindex<\/code><\/li>\n<\/ul>\n\n\n\n
      \u793a\u4f8b\uff1a<\/h3>\n\n\n\n
      local<\/strong> t = { x = 1 }\nlocal<\/strong> mt = {\n    __index = function<\/strong>() return<\/strong> \"from __index\" end<\/strong>,\n    __newindex = function<\/strong>() error(\"\u7981\u6b62\u5199\u5165\") end<\/strong>\n}\nsetmetatable(t, mt)\n\nprint(t.y)           -- \"from __index\"\nprint(rawget(t, \"y\")) -- nil\uff08\u76f4\u63a5\u8bfb\uff0c\u4e0d\u89e6\u53d1 __index\uff09\n\n-- t.z = 99         -- \u4f1a\u62a5\u9519\uff1a\u7981\u6b62\u5199\u5165\nrawset(t, \"z\", 99)   -- \u2705 \u6210\u529f\uff0c\u7ed5\u8fc7 __newindex\nprint(t.z)           -- 99<\/code><\/pre>\n\n\n\n
      \n
      \u8fd9\u4e24\u4e2a\u51fd\u6570\u5728\u5143\u65b9\u6cd5\u5185\u90e8\u64cd\u4f5c\u8868\u65f6\u5c24\u5176\u91cd\u8981\uff0c\u53ef\u4ee5\u907f\u514d\u89e6\u53d1\u5143\u8868\u5bfc\u81f4\u7684\u9012\u5f52\u6216\u526f\u4f5c\u7528\u3002<\/p>\n<\/blockquote>\n\n\n\n
      \n\n\n\n
      \u56db\u3001\u5e38\u89c1\u4f7f\u7528\u573a\u666f\u5c0f\u7ed3<\/h2>\n\n\n\n
      \u573a\u666f<\/th>\u63a8\u8350\u65b9\u6848<\/th><\/tr><\/thead>
      \u63d0\u4f9b\u9ed8\u8ba4\u503c\u6216\u5b9e\u73b0\u7ee7\u627f<\/td>__index = \u8868<\/code><\/td><\/tr>
      \u62e6\u622a\u8bfb\u53d6\u505a\u65e5\u5fd7\u6216\u8ba1\u7b97<\/td>__index = \u51fd\u6570<\/code><\/td><\/tr>
      \u5b9e\u73b0\u53ea\u8bfb\u8868<\/td>__newindex = \u62a5\u9519\u51fd\u6570<\/code><\/td><\/tr>
      \u6570\u636e\u6821\u9a8c\u6216\u5c5e\u6027\u5c01\u88c5<\/td>__newindex = \u6821\u9a8c\u51fd\u6570 + rawset<\/code><\/td><\/tr>
      \u907f\u514d\u5143\u8868\u5e72\u6270\u6216\u9012\u5f52<\/td>\u4f7f\u7528 rawget<\/code> \/ rawset<\/code><\/td><\/tr>
      \u5728\u5143\u65b9\u6cd5\u5185\u90e8\u5b89\u5168\u8bfb\u5199\u8868<\/td>\u5fc5\u987b\u4f7f\u7528 rawget<\/code> \/ rawset<\/code><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
      \n\n\n\n
      \u4e94\u3001\u6ce8\u610f\u4e8b\u9879<\/h2>\n\n\n\n
        \n
      1. __index<\/code> \u548c __newindex<\/code> \u53ea\u5bf9\u201c\u4e0d\u5b58\u5728\u7684\u952e\u201d\u751f\u6548<\/strong>\u3002<\/li>\n\n\n\n
      2. \u5728 __index<\/code> \u6216 __newindex<\/code> \u51fd\u6570\u4e2d\u64cd\u4f5c\u8868\u65f6\uff0c\u52a1\u5fc5\u4f7f\u7528 rawget<\/code> \/ rawset<\/code><\/strong>\uff0c\u5426\u5219\u53ef\u80fd\u89e6\u53d1\u9012\u5f52\u3002<\/li>\n\n\n\n
      3. \u5143\u65b9\u6cd5\u4e0d\u4f1a\u88ab\u7ee7\u627f<\/strong> \u2014\u2014 \u5b50\u8868\u5fc5\u987b\u663e\u5f0f\u8bbe\u7f6e\u81ea\u5df1\u7684\u5143\u8868\u3002<\/li>\n\n\n\n
      4. \u6027\u80fd\u654f\u611f\u7684\u4ee3\u7801\u4e2d\uff0c\u9891\u7e41\u89e6\u53d1\u5143\u65b9\u6cd5\u4f1a\u6709\u5f00\u9500\uff0c\u53ef\u8003\u8651\u7528 rawget<\/code> \/ rawset<\/code> \u4f18\u5316\u3002<\/li>\n<\/ol>\n\n\n\n
        \n\n\n\n
        \u603b\u7ed3<\/h2>\n\n\n\n
        __index<\/code>\u3001__newindex<\/code>\u3001rawget<\/code>\u3001rawset<\/code> \u662f Lua \u5143\u8868\u673a\u5236\u4e2d\u6700\u57fa\u7840\u4e5f\u6700\u5b9e\u7528\u7684\u7ec4\u6210\u90e8\u5206\u3002\u5b83\u4eec\u4e0d\u590d\u6742\uff0c\u4f46\u5728\u6784\u5efa\u914d\u7f6e\u7cfb\u7edf\u3001\u5bf9\u8c61\u6a21\u578b\u3001\u6570\u636e\u4ee3\u7406\u3001\u8c03\u8bd5\u5de5\u5177\u65f6\u975e\u5e38\u6709\u7528\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
        \u5728 Lua \u4e2d\uff0c\u8868\uff08table\uff09\u662f\u6700\u6838\u5fc3\u7684\u6570\u636e\u7ed3\u6784\u3002\u901a\u8fc7\u4e3a\u5176\u8bbe\u7f6e\u201c\u5143\u8868\u201d\uff08metatable\uff09\uff0c\u6211\u4eec\u53ef\u4ee5\u6539\u53d8\u8868 […]<\/p>\n","protected":false},"author":1,"featured_media":2330,"comment_status":"open","ping_status":"open","sticky":false,"template":"wp-custom-template-my","format":"standard","meta":{"footnotes":""},"categories":[695,154],"tags":[690,691,692,693],"class_list":["post-2338","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-lua","category-154","tag-lua","tag-metatable","tag-692","tag-693"],"_links":{"self":[{"href":"https:\/\/www.madbull.site\/index.php?rest_route=\/wp\/v2\/posts\/2338","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madbull.site\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madbull.site\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madbull.site\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madbull.site\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2338"}],"version-history":[{"count":2,"href":"https:\/\/www.madbull.site\/index.php?rest_route=\/wp\/v2\/posts\/2338\/revisions"}],"predecessor-version":[{"id":2354,"href":"https:\/\/www.madbull.site\/index.php?rest_route=\/wp\/v2\/posts\/2338\/revisions\/2354"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.madbull.site\/index.php?rest_route=\/wp\/v2\/media\/2330"}],"wp:attachment":[{"href":"https:\/\/www.madbull.site\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2338"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madbull.site\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2338"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madbull.site\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2338"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}