{"id":213,"date":"2015-04-14T17:16:41","date_gmt":"2015-04-14T09:16:41","guid":{"rendered":"http:\/\/www.cclo.idv.tw:8080\/blogs\/wordpress\/?p=213"},"modified":"2021-11-15T15:45:40","modified_gmt":"2021-11-15T07:45:40","slug":"c11-ranged-for-loop","status":"publish","type":"post","link":"https:\/\/blog.cclo.idv.tw\/?p=213","title":{"rendered":"[C++11] Ranged For Loop"},"content":{"rendered":"\n

\u5728\u4ee5\u524d\uff0c\u82e5\u662f\u6211\u5011\u8981\u91dd\u5c0d STL container \u4e2d\u7684\u6240\u6709\u7269\u4ef6\u505a\u4e8b\u60c5\uff0c\u6700\u300c\u65b9\u4fbf\u300d\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 iterator \u642d\u914d\u50b3\u7d71\u7684 for-loop\uff1a<\/p>\n\n\n\n

class Entry;\nlist<Entry> my_list;\n\nvoid check_entries(void)\n{\n    for ( list::iterator<Entry> itor = my_list.begin(); itor != my_list.end(); ++itor)\n    {\n        Entry& e = *itor; \/\/ iterator \u672c\u8eab\u7684\u64cd\u4f5c\u985e\u4f3c pointer\n        \/\/ do something...\n    }\n}<\/code><\/pre>\n\n\n\n\n\n\n\n
\u90a3\u884c for<\/code> \u7684\u6558\u8ff0\u5f0f\u771f\u662f\u53c8\u81ed\u53c8\u9577\u3002\u5373\u4f7f\u662f C++11 \u5c0e\u5165\u4e86 auto<\/code> \u95dc\u9375\u5b57\uff0c\u53ef\u4ee5\u7528\u4f86\u53d6\u4ee3 itor<\/code> \u524d\u9762\u7684\u578b\u5225\uff0c\u6574\u9ad4\u7684\u53ef\u8b80\u6027\u9084\u662f\u5f88\u5dee\u3002<\/p>\n\n\n\n
\u5e78\u597d\uff0cC++11 \u540c\u6642\u5c0e\u5165\u4e86\u5176\u4ed6\u9ad8\u968e\u8a9e\u8a00\u5e38\u898b\u7684 ranged for-loop\uff0c\u53ef\u4ee5\u589e\u52a0\u53ef\u8b80\u6027\uff0c\u4e5f\u4e0d\u7528\u518d key \u90a3\u9ebc\u591a\u56c9\u55e6\u7684\u7a0b\u5f0f\u78bc\u4e86\uff1a<\/p>\n\n\n\n
void check_entries(void)\n{\n    for ( auto& e : my_list)\n    {\n        \/\/ do something...\n    }\n}<\/code><\/pre>\n\n\n\n
\u4f7f\u7528\u4e0a\u6709\u5e7e\u500b\u9700\u8981\u6ce8\u610f\u7684\u5730\u65b9\uff1a<\/p>\n\n\n\n
  1. \u5143\u7d20 e<\/code> \u7684\u4f5c\u7528\u7bc4\u570d (scope) \u50c5\u5728 for-loop \u4e2d\u3002\u51fa\u4e86 for-loop \u5c31\u4e0d\u80fd\u7528\u4e86\uff08\u9019\u662f\u512a\u9ede\uff09\u3002<\/li>
  2. \u82e5\u662f\u578b\u5225\u7684\u5f8c\u9762\u6c92\u6709 reference \u7b26\u865f &<\/code>\uff0c\u90a3\u9ebc e<\/code> \u5c31\u662f\u300c\u8907\u88fd\u51fa\u4f86\u300d\u7684\u7269\u4ef6\uff0c\u985e\u4f3c C\/C++ \u4e2d call by value \u7684\u6982\u5ff5\u3002\u6b64\u6642 e<\/code> \u662f\u4e0d\u80fd\u4fee\u6539\u7684\uff08\u6216\u8005\u8aaa\uff1a\u5c31\u7b97\u4fee\u6539\u4e86\uff0c\u4e5f\u4e0d\u6703\u5f71\u97ff\u5230 my_list<\/code> \u4e2d\u5c0d\u61c9\u7269\u4ef6\u7684\u5167\u5bb9\uff09\u3002\u82e5\u662f\u9700\u8981\u4fee\u6539\uff0c\u5c31\u8981\u52a0\u4e0a &<\/code>\u3002<\/li>
  3. \u52a0\u4e0a &<\/code> \u9084\u6709\u4e00\u500b\u512a\u9ede\uff0c\u90a3\u5c31\u662f\u4e0d\u9700\u8981\u8907\u88fd\u6574\u500b\u7269\u4ef6\u3002\u9019\u5c0d\u65bc\u5360\u7528\u7a7a\u9593\u8f03\u5927\u7684\u7269\u4ef6\uff08\u901a\u5e38\u662f\u4f7f\u7528\u8005\u5b9a\u7fa9\u7684 class \u751f\u51fa\u4f86\u7684\u7269\u4ef6\uff09\u4f86\u8aaa\u6bd4\u8f03\u6709\u6548\u7387\u3002<\/li>
  4. \u82e5\u662f\u9700\u8981\u6548\u7387\uff0c\u53c8\u5e0c\u671b\u4fdd\u6709\u300c\u552f\u8b80\u300d\u7684\u7279\u6027\uff0c\u53ef\u4ee5\u5728\u578b\u5225\u524d\u9762\u52a0\u4e0a const<\/code>\u3002\u4ee5\u6b64\u4f8b\u4f86\u8aaa\uff0c\u5c31\u662f\u8b8a\u6210\uff1afor (const auto& e : my_list)<\/code>\u3002<\/li><\/ol>\n","protected":false},"excerpt":{"rendered":"
    \u5728\u4ee5\u524d\uff0c\u82e5\u662f\u6211\u5011\u8981\u91dd\u5c0d STL container \u4e2d\u7684\u6240\u6709\u7269\u4ef6\u505a\u4e8b\u60c5\uff0c\u6700\u300c\u65b9\u4fbf\u300d\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 iterato […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[13],"tags":[23,24],"table_tags":[],"class_list":["post-213","post","type-post","status-publish","format-standard","hentry","category--computer-science","tag-c-2","tag-c11"],"aioseo_notices":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=\/wp\/v2\/posts\/213","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=213"}],"version-history":[{"count":1,"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=\/wp\/v2\/posts\/213\/revisions"}],"predecessor-version":[{"id":578,"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=\/wp\/v2\/posts\/213\/revisions\/578"}],"wp:attachment":[{"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=213"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=213"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=213"},{"taxonomy":"table_tags","embeddable":true,"href":"https:\/\/blog.cclo.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Ftable_tags&post=213"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}