{"id":28,"date":"2007-05-22T02:45:21","date_gmt":"2007-05-22T06:45:21","guid":{"rendered":"http:\/\/prglab.com\/blog\/p\/28"},"modified":"2007-07-30T15:24:18","modified_gmt":"2007-07-30T19:24:18","slug":"references-vs-pointers","status":"publish","type":"post","link":"https:\/\/www.prglab.com\/blog\/p\/28","title":{"rendered":"C++\u4e2dReference\u4e0e\u6307\u9488\uff08Pointer\uff09\u7684\u4f7f\u7528\u5bf9\u6bd4"},"content":{"rendered":"

\u5f15\u7528(reference)\u548c\u6307\u9488(pointer)\u662f\u5b66C++\u8fc7\u7a0b\u4e2d\u6700\u4ee4\u4eba\u5934\u75bc\u7684\u95ee\u9898\uff0c\u5e38\u5e38\u4e0d\u77e5\u9053\u4ec0\u4e48\u65f6\u5019\u7528\u54ea\u4e2a\u5408\u9002\uff0c\u53c8\u5e38\u5e38\u5f04\u6df7\u3002\u627e\u5230Dan Saks\u7684\u8fd9\u7bc7\u6587\u7ae0\uff0c\u8bb2\u7684\u5f88\u6e05\u695a\uff0c\u5f3a\u70c8\u63a8\u8350\uff0c\u6240\u4ee5\u7ffb\u8bd1\u4e00\u4e0b\u4f9b\u5927\u5bb6\u53c2\u8003\u3002<\/p>\n

———————————————————————————
\n\u4ee5\u4e0b\u8bd1\u81eaDan Saks\u7684\u6587\u7ae0 References vs. Pointers \u82f1\u6587\u539f\u6587<\/a>
\n———————————————————————————<\/p>\n

\u4e86\u89e3\u5f15\u7528reference\u4e0e\u6307\u9488pointer\u5230\u5e95\u6709\u4ec0\u4e48\u4e0d\u540c\u53ef\u4ee5\u5e2e\u52a9\u4f60\u51b3\u5b9a\u4ec0\u4e48\u65f6\u5019\u8be5\u7528reference\uff0c\u4ec0\u4e48\u65f6\u5019\u8be5\u7528pointer\u3002<\/strong><\/p>\n

\u5728C++ \u4e2d\uff0creference\u5728\u5f88\u591a\u65b9\u9762\u4e0e\u6307\u9488(pointer)\u5177\u6709\u540c\u6837\u7684\u80fd\u529b\u3002\u867d\u7136\u591a\u6570C++\u7a0b\u5e8f\u5458\u5bf9\u4e8e\u4f55\u65f6\u4f7f\u7528reference\u4f55\u65f6\u4f7f\u7528pointer \u90fd\u4f1a\u6709\u4e00\u4e9b\u76f4\u89c9\uff0c\u4f46\u603b\u8fd8\u662f\u4f1a\u6709\u4e9b\u65f6\u5019\u641e\u4e0d\u6e05\u695a\u3002\u5982\u679c\u4f60\u60f3\u8981\u5efa\u7acb\u4e00\u4e2a\u5173\u4e8e\u4f7f\u7528reference\u4f7f\u7528\u7684\u6e05\u6670\u6709\u7406\u7684\u6982\u5ff5\uff0c \u53c8\u6709\u5fc5\u8981\u4e86\u89e3\u5230\u5e95reference\u548cpointer\u6709\u4ec0\u4e48\u4e0d\u540c\u3002<\/p>\n

\u6df1\u5c42\u542b\u4e49<\/h2>\n

\u4e0epointer \u7c7b\u4f3c\uff0c\u4e00\u4e2areference\u662f\u4e00\u4e2a\u5bf9\u8c61(object)\uff0c\u53ef\u4ee5\u7528\u6765\u95f4\u63a5\u6307\u5411\u53e6\u4e00\u4e2a\u5bf9\u8c61\u3002\u4e00\u4e2areference\u7684\u58f0\u660e\u4e0epointer\u7684\u58f0\u660e\u7684\u5b9e\u8d28\u8bed\u6cd5\u7ed3\u6784\u662f\u76f8\u540c\u7684\u3002\u4e0d\u540c\u7684\u662f\uff0c\u58f0\u660epointer\u7684\u65f6\u5019\u4f7f\u7528\u661f\u53f7\u64cd\u4f5c\u7b26 * \uff0c \u800c\u58f0\u660ereference\u7684\u65f6\u5019\u4f7f\u7528\u5730\u5740\u64cd\u4f5c\u7b26 & \u3002 \u4f8b\u5982\uff0c\u6211\u4eec\u6709:
\nint i = 3;<\/strong>
\n\u5219\u6709:
\nint *pi = &i;<\/strong>
\n\u58f0\u660e pi \u4e3a\u4e00\u4e2a\u6307\u9488\u7c7b\u578b\u7684\u5bf9\u8c61\uff0c\u5e76\u4e14\u662f\u4e00\u4e2a”\u6307\u5411int\u6574\u578b\u7684\u6307\u9488”\uff0c\u5b83\u7684\u521d\u59cb\u503c\u4e3a\u5bf9\u8c61i\u7684\u5730\u5740\u3002\u800c\u53e6\u4e00\u65b9\u9762\uff1a
\nint &ri = i;<\/strong>
\n\u58f0\u660e ri\u4e3a\u4e00\u4e2areference\u7c7b\u578b\u7684\u5bf9\u8c61\uff0c\u5e76\u4e14\u4e5f\u662f\u4e00\u4e2a\u6307\u5411\u6574\u578b\u7684reference\uff0c\u5b83\u6307\u5411\u7684\u662fi\u3002 \u6211\u4eec\u53ef\u4ee5\u770b\u5230pointer\u548creference\u7684\u58f0\u660e\u6709\u663e\u8457\u7684\u4e0d\u540c\uff0c\u4f46\u8fd9\u5e76\u4e0d\u662f\u51b3\u5b9a\u4f55\u65f6\u4f7f\u7528\u54ea\u4e00\u4e2a\u7684\u6839\u636e\u3002\u51b3\u5b9a\u7684\u771f\u6b63\u4f9d\u636e\u662f\u5f53\u5b83\u4eec\u88ab\u7528\u5728\u8868\u8fbe\u5f0f\u4e2d\u65f6\u5176\u663e \u793a\u7684\u4e0d\u540c\u51b3\u5b9a\u4e86\u4f7f\u7528\u54ea\u4e00\u4e2a\u5408\u9002<\/p>\n

Pointer \u548creference\u7684\u6700\u5927\u4e0d\u540c\u662f\uff1apointer\u5fc5\u987b\u4f7f\u7528\u4e00\u4e2a\u661f\u53f7\u64cd\u4f5c\u7b26 * \u6765\u53bb\u6389reference \uff08\u82f1\u6587\u53eb\u505adereference\uff0c\u6211\u4e0d\u77e5\u9053\u8fd9\u91cc\u600e\u6837\u7ffb\u8bd1\u8fd9\u4e2a\u8bcd\u5408\u9002\uff0c\u59d1\u4e14\u5c31\u53eb\u201c\u53bb\u53c2\u8003\u201d\u5427<\/font>\uff09\u800creference\u4e0d\u9700\u8981\u4efb\u4f55\u64cd\u4f5c\u7b26\u6765\u53bb\u53c2\u8003\u3002 \u4f8b\u5982\uff0c \u6709\u4e86\u4e0a\u9762\u4f8b\u5b50\u4e2d\u7684\u5b9a\u4e49\uff0c \u95f4\u63a5\u8868\u8fbe\u5f0f *pi \u5c06 pi \u53bb\u53c2\u8003\u4e3a\u6307\u5411i\u3002\u76f8\u53cd\uff0c \u8868\u8fbe\u5f0fri-\u4e0d\u9700\u8981\u4efb\u4f55\u64cd\u4f5c\u7b26-\u81ea\u52a8\u5c06ri\u53bb\u53c2\u8003\u4e3a\u6307\u5411i\u3002\u56e0\u6b64\uff0c \u4f7f\u7528\u6307\u9488p\uff0c\u6211\u4eec\u9700\u8981\u7528\u8d4b\u503c\u8bed\u53e5:
\n*p = 4; <\/strong>
\n\u5c06i\u7684\u503c\u53d8\u4e3a4\uff1b \u800c\u4f7f\u7528reference ri\uff0c\u6211\u4eec\u53ea\u9700\u8981\u76f4\u63a5\u5199\uff1a
\nri = 4; <\/strong>
\n\u5c31\u53ef\u4ee5\u540c\u6837\u5c06i\u7684\u503c\u53d8\u4e3a4 \u3002<\/p>\n

\u8fd9\u4e2a\u663e\u793a\u7684\u4e0d\u540c\u5728\u5f53\u4f60\u4e3a\u51fd\u6570\u7684\u53c2\u6570\u7c7b\u578b\u548c\u8fd4\u56de\u503c\u7c7b\u578b\u9009\u62e9\u662f\u4f7f\u7528pointer\u8fd8\u662freference\u7684\u65f6\u5019\u5c31\u4f1a\u663e\u8457\u8d77\u6765\uff0c\u5c24\u5176\u662f\u5bf9\u4e8e\u91cd\u8f7d\u64cd\u4f5c\u7b26\u7684\u51fd\u6570\u3002<\/p>\n

\u4e0b\u9762\u4f7f\u7528\u4e00\u4e2a\u9488\u5bf9\u5217\u4e3e\u7c7b\u578b\uff08enumeration\uff09\u7684++\u64cd\u4f5c\u7b26\u4f8b\u5b50\u6765\u8bf4\u660e\u4e0a\u9762\u8fd9\u70b9\u3002\u5728C++\u4e2d\uff0c \u5185\u7f6e\u7684++\u64cd\u4f5c\u7b26\u5bf9\u5217\u4e3e\u7c7b\u578b\u65e0\u6548\uff0c\u4f8b\u5982\uff0c \u5bf9\u4e0b\u9762\u5b9a\u4e49\uff1a<\/p>\n

enum day{
\nSunday, Monday, …
\n};
\nday x;<\/p><\/blockquote>\n

\u8868\u8fbe\u5f0f ++x \u4e0d\u80fd\u7f16\u8bd1\u3002\u5982\u679c\u60f3\u8ba9\u5b83\u901a\u8fc7\u7f16\u8bd1\uff0c\u5fc5\u987b\u8981\u5b9a\u4e49\u4e00\u4e2a\u540d\u4e3aoperator++\u7684\u51fd\u6570\uff0c\u63a5\u53d7day\u4e3a\u53c2\u6570\uff0c\u5e76\u4e14\u8c03\u7528 ++x \u5fc5\u987b\u6539\u53d8x\u7684\u503c\u3002\u56e0\u6b64\uff0c \u4ec5\u58f0\u660e\u4e00\u4e2a\u51fd\u6570 operator++ \uff0c \u4ee5\u7c7b\u578bday\u4e3a\u53c2\u6570\uff0c \u5982\u4e0b:
\nday operator++(day d);<\/strong>
\n\u5e76\u4e0d<\/strong>\u80fd\u591f\u5f97\u5230\u60f3\u8981\u5f97\u6548\u679c\u3002 \u8fd9\u4e2a\u51fd\u6570\u901a\u8fc7\u503c\u4f20\u9012\u53c2\u6570(pass by value)\uff0c\u8fd9\u5c31\u610f\u5473\u7740\u51fd\u6570\u5185\u770b\u5230\u7684\u662f\u53c2\u6570\u7684\u4e00\u4e2a\u62f7\u8d1d\uff0c\u800c\u4e0d\u662f\u53c2\u6570\u672c\u8eab\u3002\u4e3a\u4e86\u4f7f\u51fd\u6570\u80fd\u591f\u6539\u53d8\u5176\u64cd\u4f5c\u6570(operand)\u7684\u503c\uff0c\u5b83\u5fc5\u987b\u901a\u8fc7\u6307\u9488\u6216reference\u6765\u4f20\u9012\u5176\u64cd\u4f5c\u6570\u3002<\/p>\n

\u901a\u8fc7\u6307\u9488\u4f20\u9012\u53c2\u6570(passing by pointer)\uff0c\u51fd\u6570\u5b9a\u4e49\u5982\u4e0b:
\nday *operator++(day *d);<\/strong>
\n\u5b83\u901a\u8fc7\u5c06\u589e\u52a0\u540e\u7684\u503c\u5b58\u50a8\u5230*d\u91cc\u9762\u6765\u4f7f\u51fd\u6570\u6539\u53d8\u65e5\u671f(day)\u7684\u503c\u3002\u4f46\u662f\uff0c\u8fd9\u6837\u4f60\u5c31\u5fc5\u987b\u4f7f\u7528\u50cf\u8868\u8fbe\u5f0f++&x\u8fd9\u6837\u6765\u8c03\u7528\u8fd9\u4e2a\u64cd\u4f5c\u7b26\uff0c\u8fd9\u770b\u8d77\u6765\u4e0d\u592a\u5bf9\u52b2\u513f\u3002<\/p>\n

\u6b63\u786e\u7684\u65b9\u6cd5\u662f\u5b9a\u4e49operator++\u4ee5reference\u4e3a\u53c2\u6570\u7c7b\u578b\uff0c\u5982\u4e0b:<\/p>\n

day &operator++(day &d)
\n{
\nd = (day)(d + 1);
\nreturn d;
\n}<\/p><\/blockquote>\n

\u4f7f\u7528\u8fd9\u4e2a\u51fd\u6570\uff0c \u8868\u8fbe\u5f0f ++x \u624d\u6709\u6b63\u786e\u7684\u663e\u793a\u4ee5\u53ca\u6b63\u786e\u7684\u64cd\u4f5c\u3002<\/p>\n

Passing by reference\u4e0d\u4ec5\u4ec5\u662f\u5199operator++\u8f83\u597d\u7684\u65b9\u6cd5\uff0c\u800c\u662f\u552f\u4e00\u7684\u65b9\u6cd5\u3002 C++\u5728\u8fd9\u91cc\u5e76\u6ca1\u6709\u7ed9\u6211\u4eec\u9009\u62e9\u7684\u4f59\u5730\u3002 \u50cf\u4e0b\u9762\u7684\u58f0\u660e:
\nday *operator++(day *d);<\/strong>
\n\u662f\u4e0d\u80fd \u901a\u8fc7\u7f16\u8bd1\u7684\u3002\u6bcf\u4e2a\u91cd\u8f7d\u7684\u64cd\u4f5c\u7b26\u51fd\u6570\u5fc5\u987b\u6216\u8005\u662f\u4e00\u4e2a\u7c7b\u7684\u6210\u5458\uff0c \u6216\u8005\u4f7f\u7528\u7c7b\u578bT\u3001 T & \u6216 T const & \u4e3a\u53c2\u6570\u7c7b\u578b\uff0c\u8fd9\u91ccT\u662f\u4e00\u4e2a\u7c7b(class)\u6216\u5217\u4e3e(enumeration)\u7c7b\u578b\u3002 \u4e5f\u5c31\u662f\u8bf4\uff0c\u6bcf\u4e00\u4e2a\u91cd\u8f7d\u64cd\u4f5c\u7b26\u5fc5\u987b\u4ee5\u7c7b\u6216\u5217\u4e3e\u7c7b\u578b\u4e3a\u53c2\u6570\u7c7b\u578b\u3002\u6307\u9488\uff0c\u5373\u4f7f\u662f\u6307\u5411\u4e00\u4e2a\u7c7b\u6216\u5217\u4e3e\u7c7b\u578b\u5bf9\u8c61\u7684\u6307\u9488\uff0c\u4e5f\u4e0d\u53ef\u4ee5\u7528\u3002C++ \u4e0d\u5141\u8bb8\u5728\u91cd\u8f7d\u64cd\u4f5c\u7b26\u65f6\u91cd\u65b0\u5b9a\u4e49\u5185\u7f6e\u64cd\u4f5c\u7b26\u7684\u542b\u4e49\uff0c\u5305\u62ec\u6307\u9488\u7c7b\u578b\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u4e0d\u53ef\u4ee5\u5b9a\u4e49\uff1a
\nint operator++(int i); \/\/ \u9519\u8bef<\/strong>
\n\u56e0\u4e3a\u5b83\u8bd5\u56fe\u5bf9int\u91cd\u65b0\u5b9a\u4e49\u64cd\u4f5c\u7b26 ++ \u7684\u542b\u4e49\u3002 \u6211\u4eec\u4e5f\u4e0d\u53ef\u4ee5\u5b9a\u4e49\uff1a
\nint *operator++(int *i); \/\/ \u9519\u8bef<\/strong>
\n\u56e0\u4e3a\u5b83\u8bd5\u56fe\u5bf9 int * \u91cd\u65b0\u5b9a\u4e49\u64cd\u4f5c\u7b26 ++ \u7684\u542b\u4e49\u3002<\/p>\n

References vs. const pointers<\/h2>\n

C++ \u4e2d\u4e0d\u5141\u8bb8\u5b9a\u4e49”const reference”\uff0c \u56e0\u4e3a\u4e00\u4e2areference\u5929\u751f\u5c31\u662fconst\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u4e00\u65e6\u5c06\u4e00\u4e2areference\u7ed1\u5b9a\u5230\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5c31\u65e0\u6cd5\u518d\u5c06\u5b83\u91cd\u65b0\u7ed1\u5b9a\u5230\u53e6\u4e00\u4e2a\u4e0d\u540c\u7684\u5bf9\u8c61\u3002\u5728\u58f0 \u660e\u4e00\u4e2areference\u4e4b\u540e\u6ca1\u6709\u5199\u6cd5\u53ef\u4ee5\u5c06\u5b83\u91cd\u65b0\u7ed1\u5b9a\u5230\u53e6\u5916\u4e00\u4e2a\u5bf9\u8c61\u3002\u4f8b\u5982\uff1a
\nint &ri = i;<\/strong>
\n\u5c06 ri \u7ed1\u5b9a\u5230 i \u3002\u7136\u540e\u4e0b\u9762\u7684\u8d4b\u503c:
\nri = j;<\/strong>
\n\u5e76\u4e0d\u662f\u628a ri \u7ed1\u5b9a\u5230 j \uff0c\u800c\u662f\u5c06 j \u4e2d\u7684\u503c\u8d4b\u7ed9 ri \u6307\u5411\u7684\u5bf9\u8c61\uff0c\u4e5f\u5c31\u662f\u8d4b\u7ed9 i \u3002<\/p>\n

\u7b80\u800c\u8a00\u4e4b\uff0c\u4e00\u4e2apointer\u5728\u5b83\u7684\u6709\u751f\u4e4b\u5e74\u53ef\u4ee5\u6307\u5411\u8bb8\u591a\u4e0d\u540c\u7684\u5bf9\u8c61\uff0c\u800c\u4e00\u4e2areference\u53ea\u80fd\u591f\u6307\u5411\u4e00\u4e2a\u5bf9\u8c61\u3002\u6709\u4e9b\u4eba\u8ba4\u4e3a\u8fd9\u624d\u662f reference\u548c pointer\u6700\u5927\u7684\u4e0d\u540c\u3002\u6211\u5e76\u4e0d\u8d5e\u6210\u3002\u4e5f\u8bb8\u8fd9\u662freference\u4e0epointer\u7684\u4e00\u70b9\u4e0d\u540c\uff0c \u4f46\u5e76\u4e0d\u662freference\u548cconst pointer\u7684\u4e0d\u540c\u3002\u5728\u5f3a\u8c03\u4e00\u904d\uff0c\u4e00\u65e6\u4e00\u4e2areference\u4e0e\u4e00\u4e2a\u5bf9\u8c61\u7ed1\u5b9a\uff0c\u5c31\u4e0d\u80fd\u518d\u5c06\u5b83\u6539\u6307\u5411\u53e6\u5916\u7684\u4e1c\u897f\u3002\u65e2\u7136\u4e0d\u80fd\u518d\u7ed1\u5b9areference\u4e4b\u540e\u518d \u6539\u53d8\uff0c \u4e00\u4e2areference\u5c31\u5fc5\u987b\u5728\u4e00\u51fa\u751f\u5c31\u88ab\u7ed1\u5b9a\u3002\u5426\u5219\u8fd9\u4e2areference\u5c31\u6c38\u8fdc\u4e0d\u80fd\u88ab\u7ed1\u5b9a\u5230\u4efb\u4f55\u4e1c\u897f\uff0c\u4e5f\u5c31\u6beb\u65e0\u7528\u5904\u4e86\u3002<\/p>\n

\u4e0a\u4e00\u6bb5\u7684\u8ba8\u8bba\u4e5f\u540c\u6837\u5b8c\u5168\u9002\u7528\u4e8e\u5e38\u91cf\u6307\u9488\uff08const pointer\uff09\u3002\uff08\u6ce8\u610f\uff0c\u6211\u8fd9\u91cc\u8bf4\u7684\u662f\u5e38\u91cf\u6307\u9488\uff08const pointer\uff09\uff0c \u800c\u4e0d\u662f\u6307\u5411\u5e38\u91cf\u7684\u6307\u9488 “pointers to const”\u3002) \u4f8b\u5982\uff0c\u4e00\u4e2areference\u58f0\u660e\u5fc5\u987b\u540c\u65f6\u5e26\u6709\u4e00\u4e2a\u521d\u59cb\u5316\u8d4b\u503c\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n

void f()
\n{
\nint &r = i;
\n…
\n}<\/p><\/blockquote>\n

\u7701\u7565\u8fd9\u4e2a\u521d\u59cb\u5316\u8d4b\u503c\u5c06\u4ea7\u751f\u4e00\u4e2a\u7f16\u8bd1\u9519\u8bef\uff1a<\/p>\n

void f()
\n{
\nint &r; \/\/\u9519\u8bef
\n…
\n}<\/p><\/blockquote>\n

\u4e00\u4e2a\u5e38\u91cf\u6307\u9488\u7684\u58f0\u660e\u4e5f\u540c\u6837\u5fc5\u987b\u5e26\u6709\u4e00\u4e2a\u521d\u59cb\u5316\u8d4b\u503c\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n

void f()
\n{
\nint *const p = &i;
\n…
\n}<\/p><\/blockquote>\n

\u7701\u7565\u8fd9\u4e2a\u521d\u59cb\u5316\u8d4b\u503c\u540c\u6837\u4f1a\u51fa\u9519\uff1a<\/p>\n

void f(){
\nint *const p; \/\/ \u9519\u8bef
\n…
\n}<\/p><\/blockquote>\n

\u5728\u6211\u770b\u6765\uff0c \u4e0d\u80fd\u591f\u5bf9reference\u4e8c\u6b21\u7ed1\u5b9a\u4f5c\u4e3areference\u4e0epointer\u7684\u4e0d\u540c\u3002\u5e76\u4e0d\u6bd4\u5e38\u91cf\u6307\u9488\u548c\u975e\u5e38\u91cf\u6307\u9488\u7684\u4e0d\u540c\u66f4\u4e3a\u663e\u8457\u3002<\/p>\n

Null references<\/h2>\n

\u9664\u4e86\u663e\u793a\u7684\u4e0d\u540c\uff0c\u5e38\u91cf\u6307\u9488\u4e0ereference\u8fd8\u6709\u4e00\u70b9\u975e\u5e38\u4e0d\u540c\uff0c\u90a3\u5c31\u662f\uff0c\u4e00\u4e2a\u6709\u6548\u7684reference\u5fc5\u987b\u6307\u5411\u4e00\u4e2a\u5bf9\u8c61\uff1b\u800c\u4e00\u4e2a\u6307\u9488\u4e0d\u9700\u8981\u3002\u4e00\u4e2a\u6307\u9488\uff0c\u5373\u4f7f\u662f\u4e00\u4e2a\u5e38\u91cf\u6307\u9488\uff0c \u90fd\u53ef\u4ee5\u6709\u7a7a\u503c\u3002 \u4e00\u4e2a\u7a7a\u6307\u9488\u4e0d\u6307\u5411\u4efb\u4f55\u4e1c\u897f\u3002<\/p>\n

\u8fd9\u70b9\u4e0d\u540c\u5c31\u6697\u793a\u5f53\u4f60\u60f3\u8981\u786e\u4fe1\u4e00\u4e2a\u53c2\u6570\u5fc5\u987b\u6307\u5411\u4e00\u4e2a\u5bf9\u8c61\u7684\u65f6\u5019\uff0c\u5e94\u8be5\u4f7f\u7528reference\u4f5c\u4e3a\u53c2\u6570\u7c7b\u578b\u3002 \u4f8b\u5982\uff0c\u4ea4\u6362\u51fd\u6570(swap function)\uff0c\u5b83\u63a5\u53d7\u4e24\u4e2aint\u53c2\u6570\uff0c\u5e76\u5c06\u4e24\u4e2a\u53c2\u6570\u7684\u6570\u503c\u5bf9\u8c03\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n

int i, j;
\nswap(i, j);<\/p><\/blockquote>\n

\u5c06\u539f\u672c\u5728 i \u4e2d\u7684\u503c\u653e\u5230 j \u4e2d\uff0c \u5e76\u5c06\u539f\u672c\u5728 j \u4e2d\u7684\u503c\u653e\u5230 i \u4e2d\u3002\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5199\u8fd9\u4e2a\u51fd\u6570\uff1a<\/p>\n

void swap(int *v1, int *v2)
\n{
\nint temp = *v1;
\n*v1 = *v2;
\n*v2 = temp;
\n}<\/p><\/blockquote>\n

\u8fd9\u79cd\u5b9a\u4e49\u4e0b\uff0c\u51fd\u6570\u8981\u50cf\u8fd9\u6837\u88ab\u8c03\u7528: swap(&i, &j);<\/strong><\/p>\n

\u8fd9\u4e2a\u63a5\u53e3\u6697\u793a\u5176\u4e2d\u4e00\u4e2a\u6216\u4e24\u4e2a\u53c2\u6570\u90fd\u6709\u53ef\u80fd\u4e3a\u7a7a(null)\u3002\u800c\u8fd9\u4e2a\u6697\u793a\u662f\u8bef\u5bfc\u7684\u3002\u4f8b\u5982\uff0c\u8c03\u7528
\nswap(&i, NULL);
\n<\/strong>\u7684\u540e\u679c\u5f88\u53ef\u80fd\u662f\u4e0d\u6109\u5feb\u7684\u3002<\/p>\n

\u800c\u50cf\u4e0b\u9762\u8fd9\u6837\u5b9a\u4e49reference\u4e3a\u53c2\u6570\uff1a<\/p>\n

void swap(int &v1, int &v2)
\n{
\nint temp = v1;
\nv1 = v2;
\nv2 = temp;
\n}<\/p><\/blockquote>\n

\u6e05\u6670\u7684\u8868\u660e\u4e86\u8c03\u7528swap\u5e94\u8be5\u63d0\u4f9b\u4e24\u4e2a\u5bf9\u8c61\uff0c\u5b83\u4eec\u7684\u503c\u5c06\u88ab\u4ea4\u6362\u3002 \u5e76\u4e14\u8fd9\u6837\u5b9a\u4e49\u7684\u53e6\u4e00\u4e2a\u597d\u5904\u662f\uff0c\u5728\u8c03\u7528\u8fd9\u4e2a\u51fd\u6570\u7684\u65f6\u5019\uff0c\u4e0d\u9700\u8981\u4f7f\u7528\u90a3\u4e9b&\u7b26\u53f7\uff0c\u770b\u8d77\u6765\u66f4\u987a\u773c\uff1a
\nswap(i, j);<\/strong><\/p>\n

\u66f4\u5b89\u5168?<\/h2>\n

\u6709\u4e9b\u4eba\u8ba4\u4e3a\u65e2\u7136reference\u4e0d\u80fd\u591f\u4e3a\u7a7a\uff0c\u90a3\u4e48\u5b83\u5e94\u8be5\u6bd4\u6307\u9488\u66f4\u5b89\u5168\u3002 \u6211\u8ba4\u4e3areference\u53ef\u80fd\u8981\u5b89\u5168\u4e00\u70b9\uff0c\u4f46\u4e0d\u4f1a\u5b89\u5168\u5f88\u591a\u3002\u867d\u7136\u4e00\u4e2a\u6709\u6548\u7684reference\u4e0d\u80fd\u4e3a\u7a7a\uff0c\u4f46\u662f\u65e0\u6548\u7684\u53ef\u4ee5\u5440\u3002\u5b9e\u9645\u4e0a\uff0c\u5728\u5f88\u591a\u60c5\u51b5\u4e0b\u7a0b\u5e8f\u6709\u53ef \u80fd\u4ea7\u751f\u65e0\u6548\u7684reference\uff0c\u800c\u4e0d\u53ea\u662f\u7a7a\u7684reference\u3002 \u4f8b\u5982\uff0c\u4f60\u53ef\u4ee5\u5b9a\u4e49\u4e00\u4e2areference\uff0c\u4f7f\u5b83\u7ed1\u5b9a\u5230\u4e00\u4e2a\u6307\u9488\u6307\u5411\u7684\u5bf9\u8c61\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n

int *p;
\n…
\nint &r = *p;<\/p><\/blockquote>\n

\u5982\u679c\u6307\u9488*p\u5728reference\u5b9a\u4e49\u65f6\u521a\u597d\u4e3a\u7a7a\uff0c\u5219\u8fd9\u4e2areference\u4e3a\u7a7a\u3002 \u4ece\u6280\u672f\u4e0a\u6765\u8bf4\uff0c\u8fd9\u4e2a\u9519\u8bef\u5e76\u4e0d\u5728\u4e8e\u5c06reference\u7ed1\u5b9a\u5230\u4e00\u4e2a\u7a7a\u503c\uff0c\u800c\u662f\u5728\u4e8e\u5bf9\u4e00\u4e2a\u7a7a\u6307\u9488\u53bb\u53c2\u8003\u3002 \u5bf9\u4e00\u4e2a\u7a7a\u6307\u9488\u53bb\u53c2\u8003\u4ea7\u751f\u4e86\u4e00\u4e2a\u4e0d\u786e\u5b9a\u7684\u64cd\u4f5c\uff0c\u4e5f\u5c31\u610f\u5473\u7740\u5f88\u591a\u4e8b\u90fd\u53ef\u80fd\u53d1\u751f\uff0c\u800c\u4e14\u5927\u90e8\u5206\u90fd\u4e0d\u662f\u4ec0\u4e48\u597d\u4e8b\u3002\u5f88\u6709\u53ef\u80fd\u5f53\u7a0b\u5e8f\u5c06reference r \u7ed1\u5b9a\u5230*p (p\u6240\u6307\u5411\u7684\u5bf9\u8c61)\u7684\u65f6\u5019\uff0cp\u5b9e\u9645\u4e0a\u6ca1\u6709\u88ab\u53bb\u53c2\u8003\uff0c\u751a\u81f3\u7a0b\u5e8f\u53ea\u662f\u5c06p\u7684\u503c\u62f7\u8d1d\u7ed9\u5b9e\u73b0r\u7684\u6307\u9488\u3002\u800c\u7a0b\u5e8f\u5c06\u4f1a\u7ee7\u7eed\u6267\u884c\u4e0b\u53bb\u76f4\u5230\u9519\u8bef\u5728\u540e\u9762\u7684\u8fd0\u884c\u4e2d\u66f4\u4e3a\u660e\u663e\u7684\u8868 \u73b0\u51fa\u6765\uff0c\u4ea7\u751f\u4e0d\u53ef\u9884\u77e5\u7684\u5371\u5bb3\u3002<\/p>\n

\u4e0b\u9762\u7684\u51fd\u6570\u5c55\u793a\u4e86\u53e6\u5916\u4e00\u79cd\u4ea7\u751f\u65e0\u6548reference\u7684\u65b9\u6cd5\uff1a<\/p>\n

int &f()
\n{
\nint i;
\n…
\nreturn i;
\n}<\/p><\/blockquote>\n

\u8fd9\u4e2a\u51fd\u6570\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u672c\u5730\u53d8\u91cf i \u7684reference\u3002\u7136\u800c\u5f53\u51fd\u6570\u8fd4\u56de\u65f6\uff0c\u672c\u5730\u53d8\u91cf i \u7684\u5b58\u50a8\u7a7a\u95f4\u4e5f\u5c31\u6d88\u5931\u4e86\u3002\u56e0\u6b64\u8fd9\u4e2a\u51fd\u6570\u5b9e\u9645\u8fd4\u56de\u4e86\u4e00\u4e2a\u6307\u5411\u88ab\u56de\u6536\u4e86\u7684\u7a7a\u95f4\u7684reference\u3002\u8fd9\u4e2a\u64cd\u4f5c\u4e0e\u8fd4\u56de\u4e00\u4e2a\u6307\u5411\u672c\u5730\u53d8\u91cf\u7684\u6307\u9488\u7684\u540e\u679c\u76f8\u540c\u3002\u6709\u4e9b\u7f16\u8bd1 \u5668\u53ef\u4ee5\u5728\u7f16\u8bd1\u65f6\u53d1\u73b0\u8fd9\u4e2a\u9519\u8bef\uff0c\u4f46\u4e5f\u5f88\u6709\u53ef\u80fd\u4e0d\u4f1a\u53d1\u73b0\u3002<\/p>\n

\u6211\u559c\u6b22reference\uff0c\u4e5f\u6709\u5f88\u597d\u7684\u7406\u7531\u4f7f\u7528\u5b83\u4eec\u4ee3\u66ffpointer\u3002\u4f46\u5982\u679c\u4f60\u671f\u671b\u4f7f\u7528reference\u6765\u4f7f\u4f60\u7684\u7a0b\u5e8f\u5065\u58ee\u6027\u663e\u8457\u589e\u5f3a\uff0c\u90a3\u4e48\u4f60\u591a\u534a\u4f1a\u5931\u671b\u7684\u3002<\/p>\n

\u53c2\u8003\u8d44\u6599\uff1a<\/h2>\n
    \n
  1. Saks, Dan. “Introduction to References<\/a>,” Embedded Systems Programming,<\/em> January 2001, p. 81.<\/li>\n
  2. Saks, Dan. “References and const<\/a>“, Embedded Systems Programming<\/em> February 2001, p. 73.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    \u5f15\u7528(reference)\u548c\u6307\u9488(pointer)\u662f\u5b66C++\u8fc7\u7a0b\u4e2d\u6700\u4ee4\u4eba\u5934\u75bc\u7684\u95ee\u9898\uff0c\u5e38\u5e38\u4e0d\u77e5\u9053\u4ec0\u4e48\u65f6\u5019\u7528\u54ea\u4e2a\u5408\u9002\uff0c\u53c8\u5e38\u5e38\u5f04\u6df7\u3002\u627e\u5230Dan Saks\u7684\u8fd9\u7bc7\u6587\u7ae0\uff0c\u8bb2\u7684\u5f88\u6e05\u695a\uff0c\u5f3a\u70c8\u63a8\u8350\uff0c\u6240\u4ee5\u7ffb\u8bd1\u4e00\u4e0b\u4f9b\u5927\u5bb6\u53c2\u8003\u3002 ——————————————————————————— \u4ee5\u4e0b\u8bd1\u81eaDan Saks\u7684\u6587\u7ae0 References vs. Pointers \u82f1\u6587\u539f\u6587 ——————————————————————————— \u4e86\u89e3\u5f15\u7528reference\u4e0e\u6307\u9488pointer\u5230\u5e95\u6709\u4ec0\u4e48\u4e0d\u540c\u53ef\u4ee5\u5e2e\u52a9\u4f60\u51b3\u5b9a\u4ec0\u4e48\u65f6\u5019\u8be5\u7528reference\uff0c\u4ec0\u4e48\u65f6\u5019\u8be5\u7528pointer\u3002 \u5728C++ \u4e2d\uff0creference\u5728\u5f88\u591a\u65b9\u9762\u4e0e\u6307\u9488(pointer)\u5177\u6709\u540c\u6837\u7684\u80fd\u529b\u3002\u867d\u7136\u591a\u6570C++\u7a0b\u5e8f\u5458\u5bf9\u4e8e\u4f55\u65f6\u4f7f\u7528reference\u4f55\u65f6\u4f7f\u7528pointer \u90fd\u4f1a\u6709\u4e00\u4e9b\u76f4\u89c9\uff0c\u4f46\u603b\u8fd8\u662f\u4f1a\u6709\u4e9b\u65f6\u5019\u641e\u4e0d\u6e05\u695a\u3002\u5982\u679c\u4f60\u60f3\u8981\u5efa\u7acb\u4e00\u4e2a\u5173\u4e8e\u4f7f\u7528reference\u4f7f\u7528\u7684\u6e05\u6670\u6709\u7406\u7684\u6982\u5ff5\uff0c \u53c8\u6709\u5fc5\u8981\u4e86\u89e3\u5230\u5e95reference\u548cpointer\u6709\u4ec0\u4e48\u4e0d\u540c\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[8],"tags":[],"_links":{"self":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/posts\/28"}],"collection":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/comments?post=28"}],"version-history":[{"count":0,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/posts\/28\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/media?parent=28"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/categories?post=28"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/tags?post=28"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}