{"id":365,"date":"2020-11-03T12:13:08","date_gmt":"2020-11-03T16:13:08","guid":{"rendered":"http:\/\/www.prglab.com\/blog\/?page_id=365"},"modified":"2020-11-03T12:13:08","modified_gmt":"2020-11-03T16:13:08","slug":"templates","status":"publish","type":"page","link":"https:\/\/www.prglab.com\/blog\/cplusplus-tutorial\/advanced-concepts\/templates","title":{"rendered":"C++\u6a21\u677f"},"content":{"rendered":"\n

5.1 \u6a21\u677f(Templates)<\/h2>\n\n\n\n

\u6a21\u677f(Templates)\u662fANSI-C++ \u6807\u51c6\u4e2d\u65b0\u5f15\u5165\u7684\u6982\u5ff5\u3002\u5982\u679c\u4f60\u4f7f\u7528\u7684 C++ \u7f16\u8bd1\u5668\u4e0d\u7b26\u5408\u8fd9\u4e2a\u6807\u51c6\uff0c\u5219\u4f60\u5f88\u53ef\u80fd\u4e0d\u80fd\u4f7f\u7528\u6a21\u677f\u3002<\/p>\n\n\n\n

\u51fd\u6570\u6a21\u677f( Function templates)<\/h3>\n\n\n\n

\u6a21\u677f(Templates)\u4f7f\u5f97\u6211\u4eec\u53ef\u4ee5\u751f\u6210\u901a\u7528\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51fd\u6570\u80fd\u591f\u63a5\u53d7\u4efb\u610f\u6570\u636e\u7c7b\u578b\u7684\u53c2\u6570\uff0c\u53ef\u8fd4\u56de\u4efb\u610f\u7c7b\u578b\u7684\u503c\uff0c\u800c\u4e0d\u9700\u8981\u5bf9\u6240\u6709\u53ef\u80fd\u7684\u6570\u636e\u7c7b\u578b\u8fdb\u884c\u51fd\u6570\u91cd\u8f7d\u3002\u8fd9\u5728\u4e00\u5b9a\u7a0b\u5ea6\u4e0a\u5b9e\u73b0\u4e86\u5b8f\uff08macro\uff09\u7684\u4f5c\u7528\u3002\u5b83\u4eec\u7684\u539f\u578b\u5b9a\u4e49\u53ef\u4ee5\u662f\u4e0b\u9762\u4e24\u79cd\u4e2d\u7684\u4efb\u4f55\u4e00\u4e2a\uff1a<\/p>\n\n\n\n

template <class identifier> function_declaration;
template <typename identifier> function_declaration;<\/code><\/p>\n\n\n\n

\u4e0a\u9762\u4e24\u79cd\u539f\u578b\u5b9a\u4e49\u7684\u4e0d\u540c\u4e4b\u5904\u5728\u5173\u952e\u5b57class \u6216 typename\u7684\u4f7f\u7528\u3002\u5b83\u4eec\u5b9e\u9645\u662f\u5b8c\u5168\u7b49\u4ef7\u7684\uff0c\u56e0\u4e3a\u4e24\u79cd\u8868\u8fbe\u7684\u610f\u601d\u548c\u6267\u884c\u90fd\u4e00\u6a21\u4e00\u6837\u3002<\/p>\n\n\n\n

\u4f8b\u5982\uff0c\u8981\u751f\u6210\u4e00\u4e2a\u6a21\u677f\uff0c\u8fd4\u56de\u4e24\u4e2a\u5bf9\u8c61\u4e2d\u8f83\u5927\u7684\u4e00\u4e2a\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5199\uff1a<\/p>\n\n\n\n

template <class GenericType><\/p>\n\n\n\n

GenericType GetMax (GenericType a, GenericType b) { return (a>b?a:b); }<\/p>\n\n\n\n

\u5728\u7b2c\u4e00\u884c\u58f0\u660e\u4e2d\uff0c\u6211\u4eec\u5df2\u7ecf\u751f\u6210\u4e86\u4e00\u4e2a\u901a\u7528\u6570\u636e\u7c7b\u578b\u7684\u6a21\u677f\uff0c\u53eb\u505aGenericType\u3002\u56e0\u6b64\u5728\u5176\u540e\u9762\u7684\u51fd\u6570\u4e2d\uff0cGenericType \u6210\u4e3a\u4e00\u4e2a\u6709\u6548\u7684\u6570\u636e\u7c7b\u578b\uff0c\u5b83\u88ab\u7528\u6765\u5b9a\u4e49\u4e86\u4e24\u4e2a\u53c2\u6570a\u548c b \uff0c\u5e76\u88ab\u7528\u4f5c\u4e86\u51fd\u6570GetMax\u7684\u8fd4\u56de\u503c\u7c7b\u578b\u3002<\/p>\n\n\n\n

GenericType \u4ecd\u6ca1\u6709\u4ee3\u8868\u4efb\u4f55\u5177\u4f53\u7684\u6570\u636e\u7c7b\u578b\uff1b\u5f53\u51fd\u6570 GetMax \u88ab\u8c03\u7528\u7684\u65f6\u5019\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u4efb\u4f55\u6709\u6548\u7684\u6570\u636e\u7c7b\u578b\u6765\u8c03\u7528\u5b83\u3002\u8fd9\u4e2a\u6570\u636e\u7c7b\u578b\u5c06\u88ab\u4f5c\u4e3apattern\u6765\u4ee3\u66ff\u51fd\u6570\u4e2dGenericType \u51fa\u73b0\u7684\u5730\u65b9\u3002\u7528\u4e00\u4e2a\u7c7b\u578bpattern\u6765\u8c03\u7528\u4e00\u4e2a\u6a21\u677f\u7684\u65b9\u6cd5\u5982\u4e0b\uff1a<\/p>\n\n\n\n

function <type> (parameters);<\/code><\/p>\n\n\n\n

\u4f8b\u5982\uff0c\u8981\u8c03\u7528GetMax \u6765\u6bd4\u8f83\u4e24\u4e2aint\u7c7b\u578b\u7684\u6574\u6570\u53ef\u4ee5\u8fd9\u6837\u5199\uff1a<\/p>\n\n\n\n

int x,y;
GetMax <int> (x,y);<\/code><\/p>\n\n\n\n

\u56e0\u6b64\uff0cGetMax \u7684\u8c03\u7528\u5c31\u597d\u50cf\u6240\u6709\u7684GenericType \u51fa\u73b0\u7684\u5730\u65b9\u90fd\u7528int \u6765\u4ee3\u66ff\u4e00\u6837\u3002<\/p>\n\n\n\n

\u8fd9\u91cc\u662f\u4e00\u4e2a\u4f8b\u5b50\uff1a<\/p>\n\n\n\n

\/\/ function template#include <iostream.h>template <class T> T GetMax (T a, T b) {    T result;    result = (a>b)? a : b;    return (result);}int main () {    int i=5, j=6, k;    long l=10, m=5, n;    k=GetMax(i,j);    n=GetMax(l,m);    cout << k << endl;    cout << n << endl;    return 0;
}<\/td>		6
10<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

(\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u5c06\u901a\u7528\u6570\u636e\u7c7b\u578b\u547d\u540d\u4e3aT \u800c\u4e0d\u662f GenericType \uff0c\u56e0\u4e3aT\u77ed\u4e00\u4e9b\uff0c\u5e76\u4e14\u5b83\u662f\u6a21\u677f\u66f4\u4e3a\u901a\u7528\u7684\u6807\u793a\u4e4b\u4e00\uff0c\u867d\u7136\u4f7f\u7528\u4efb\u4f55\u6709\u6548\u7684\u6807\u793a\u7b26\u90fd\u662f\u53ef\u4ee5\u7684\u3002)<\/p>\n\n\n\n

\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u5bf9\u540c\u6837\u7684\u51fd\u6570GetMax()\u4f7f\u7528\u4e86\u4e24\u79cd\u53c2\u6570\u7c7b\u578b\uff1aint \u548c long\uff0c\u800c\u53ea\u5199\u4e86\u4e00\u79cd\u51fd\u6570\u7684\u5b9e\u73b0\uff0c\u4e5f\u5c31\u662f\u8bf4\u6211\u4eec\u5199\u4e86\u4e00\u4e2a\u51fd\u6570\u7684\u6a21\u677f\uff0c\u7528\u4e86\u4e24\u79cd\u4e0d\u540c\u7684pattern\u6765\u8c03\u7528\u5b83\u3002<\/p>\n\n\n\n

\u5982\u4f60\u6240\u89c1\uff0c\u5728\u6211\u4eec\u7684\u6a21\u677f\u51fd\u6570 GetMax() \u91cc\uff0c\u7c7b\u578b T \u53ef\u4ee5\u88ab\u7528\u6765\u58f0\u660e\u65b0\u7684\u5bf9\u8c61<\/p>\n\n\n\n

T result;<\/code><\/p>\n\n\n\n

result \u662f\u4e00\u4e2aT\u7c7b\u578b\u7684\u5bf9\u8c61\uff0c \u5c31\u50cfa \u548c b\u4e00\u6837\uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c\u5b83\u4eec\u90fd\u662f\u540c\u4e00\u7c7b\u578b\u7684\uff0c\u8fd9\u79cd\u7c7b\u578b\u5c31\u662f\u5f53\u6211\u4eec\u8c03\u7528\u6a21\u677f\u51fd\u6570\u65f6\u5199\u5728\u5c16\u62ec\u53f7<> \u4e2d\u7684\u7c7b\u578b\u3002<\/p>\n\n\n\n

\u5728\u8fd9\u4e2a\u5177\u4f53\u7684\u4f8b\u5b50\u4e2d\uff0c\u901a\u7528\u7c7b\u578b T \u88ab\u7528\u4f5c\u51fd\u6570GetMax \u7684\u53c2\u6570\uff0c\u4e0d\u9700\u8981\u8bf4\u660e<int>\u6216 <long>\uff0c\u7f16\u8bd1\u5668\u4e5f\u53ef\u4ee5\u81ea\u52a8\u68c0\u6d4b\u5230\u4f20\u5165\u7684\u6570\u636e\u7c7b\u578b\uff0c\u56e0\u6b64\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u8fd9\u6837\u5199\u8fd9\u4e2a\u4f8b\u5b50\uff1a<\/p>\n\n\n\n

int i,j;
GetMax (i,j);<\/code><\/p>\n\n\n\n

\u56e0\u4e3ai \u548cj \u90fd\u662fint \u7c7b\u578b\uff0c\u7f16\u8bd1\u5668\u4f1a\u81ea\u52a8\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u51fd\u6570\u6309\u7167int\u8fdb\u884c\u8c03\u7528\u3002\u8fd9\u79cd\u6697\u793a\u7684\u65b9\u6cd5\u66f4\u4e3a\u6709\u7528\uff0c\u5e76\u4ea7\u751f\u540c\u6837\u7684\u7ed3\u679c\uff1a<\/p>\n\n\n\n

\/\/ function template II#include <iostream.h>template <class T> T GetMax (T a, T b) {    return (a>b?a:b);}int main () {    int i=5, j=6, k;    long l=10, m=5, n;    k=GetMax(i,j);    n=GetMax(l,m);    cout << k << endl;    cout << n << endl;    return 0;}<\/td>6
10<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

\u6ce8\u610f\u5728\u8fd9\u4e2a\u4f8b\u5b50\u7684main() \u4e2d\u6211\u4eec\u5982\u4f55\u8c03\u7528\u6a21\u677f\u51fd\u6570GetMax() \u800c\u6ca1\u6709\u5728\u62ec\u53f7<>\u4e2d\u6307\u660e\u5177\u4f53\u6570\u636e\u7c7b\u578b\u7684\u3002\u7f16\u8bd1\u5668\u81ea\u52a8\u51b3\u5b9a\u6bcf\u4e00\u4e2a\u8c03\u7528\u9700\u8981\u4ec0\u4e48\u6570\u636e\u7c7b\u578b\u3002<\/p>\n\n\n\n

\u56e0\u4e3a\u6211\u4eec\u7684\u6a21\u677f\u51fd\u6570\u53ea\u5305\u62ec\u4e00\u79cd\u6570\u636e\u7c7b\u578b (class T)\uff0c \u800c\u4e14\u5b83\u7684\u4e24\u4e2a\u53c2\u6570\u90fd\u662f\u540c\u4e00\u79cd\u7c7b\u578b\uff0c\u6211\u4eec\u4e0d\u80fd\u591f\u7528\u4e24\u4e2a\u4e0d\u540c\u7c7b\u578b\u7684\u53c2\u6570\u6765\u8c03\u7528\u5b83\uff1aint i;
long l;
k = GetMax (i,l);<\/p>\n\n\n\n

\u4e0a\u9762\u7684\u8c03\u7528\u5c31\u662f\u4e0d\u5bf9\u7684\uff0c\u56e0\u4e3a\u6211\u4eec\u7684\u51fd\u6570\u7b49\u5f85\u7684\u662f\u4e24\u4e2a\u540c\u79cd\u7c7b\u578b\u7684\u53c2\u6570\u3002<\/p>\n\n\n\n

\u6211\u4eec\u4e5f\u53ef\u4ee5\u4f7f\u5f97\u6a21\u677f\u51fd\u6570\u63a5\u53d7\u4e24\u79cd\u6216\u4e24\u79cd\u4ee5\u4e0a\u7c7b\u578b\u7684\u6570\u636e\uff0c\u4f8b\u5982\uff1a<\/p>\n\n\n\n

template <class T><\/p>\n\n\n\n

T GetMin (T a, U b) { return (a<b?a:b); }<\/p>\n\n\n\n

\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u7684\u6a21\u677f\u51fd\u6570 GetMin() \u63a5\u53d7\u4e24\u4e2a\u4e0d\u540c\u7c7b\u578b\u7684\u53c2\u6570\uff0c\u5e76\u8fd4\u56de\u4e00\u4e2a\u4e0e\u7b2c\u4e00\u4e2a\u53c2\u6570\u540c\u7c7b\u578b\u7684\u5bf9\u8c61\u3002\u5728\u8fd9\u79cd\u5b9a\u4e49\u4e0b\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u8c03\u7528\u8be5\u51fd\u6570\uff1aint i,j;
long l;
i = GetMin <int, long> (j,l);<\/p>\n\n\n\n

\u6216\u8005\uff0c\u7b80\u5355\u7684\u7528<\/p>\n\n\n\n

i = GetMin (j,l);<\/code><\/p>\n\n\n\n

\u867d\u7136 j \u548c l \u662f\u4e0d\u540c\u7684\u7c7b\u578b\u3002<\/p>\n\n\n\n

\u7c7b\u6a21\u677f(Class templates)<\/h3>\n\n\n\n

\u6211\u4eec\u4e5f\u53ef\u4ee5\u5b9a\u4e49\u7c7b\u6a21\u677f\uff08class templates\uff09\uff0c\u4f7f\u5f97\u4e00\u4e2a\u7c7b\u53ef\u4ee5\u6709\u57fa\u4e8e\u901a\u7528\u7c7b\u578b\u7684\u6210\u5458\uff0c\u800c\u4e0d\u9700\u8981\u5728\u7c7b\u751f\u6210\u7684\u65f6\u5019\u5b9a\u4e49\u5177\u4f53\u7684\u6570\u636e\u7c7b\u578b\uff0c\u4f8b\u5982\uff1a<\/p>\n\n\n\n

template <class T><\/p>\n\n\n\n

class pair {<\/p>\n\n\n\n

    T values [2];<\/p>\n\n\n\n

public:<\/p>\n\n\n\n

    pair (T first, T second) {<\/p>\n\n\n\n

        values[0]=first;<\/p>\n\n\n\n

        values[1]=second;<\/p>\n\n\n\n

    }<\/p>\n\n\n\n

};<\/p>\n\n\n\n

\u4e0a\u9762\u6211\u4eec\u5b9a\u4e49\u7684\u7c7b\u53ef\u4ee5\u7528\u6765\u5b58\u50a8\u4e24\u4e2a\u4efb\u610f\u7c7b\u578b\u7684\u5143\u7d20\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u8981\u5b9a\u4e49\u8be5\u7c7b\u7684\u4e00\u4e2a\u5bf9\u8c61\uff0c\u7528\u6765\u5b58\u50a8\u4e24\u4e2a\u6574\u578b\u6570\u636e115 \u548c 36 \uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5199\uff1a<\/p>\n\n\n\n

pair<int> myobject (115, 36);<\/code><\/p>\n\n\n\n

\u6211\u4eec\u540c\u65f6\u53ef\u4ee5\u7528\u8fd9\u4e2a\u7c7b\u6765\u751f\u6210\u53e6\u4e00\u4e2a\u5bf9\u8c61\u7528\u6765\u5b58\u50a8\u4efb\u4f55\u5176\u4ed6\u7c7b\u578b\u6570\u636e\uff0c\u4f8b\u5982\uff1a<\/p>\n\n\n\n

pair<float> myfloats (3.0, 2.18);<\/code><\/p>\n\n\n\n

\u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u7c7b\u7684\u552f\u4e00\u4e00\u4e2a\u6210\u5458\u51fd\u6570\u5df2\u7ecf\u88abinline \u5b9a\u4e49\u3002\u5982\u679c\u6211\u4eec\u8981\u5728\u7c7b\u4e4b\u5916\u5b9a\u4e49\u5b83\u7684\u4e00\u4e2a\u6210\u5458\u51fd\u6570\uff0c\u6211\u4eec\u5fc5\u987b\u5728\u6bcf\u4e00\u51fd\u6570\u524d\u9762\u52a0template <… >\u3002<\/p>\n\n\n\n

\/\/ class templates#include <iostream.h>template <class T> class pair {
     T value1, value2;
public:
    pair (T first, T second) {        value1=first;        value2=second;    }    T getmax ();};

template <class T>T pair::getmax (){    T retval;    retval = value1>value2? value1 : value2;    return retval;}

int main () {    pair myobject (100, 75);    cout << myobject.getmax();    return 0;}<\/td>		100<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

\u6ce8\u610f\u6210\u5458\u51fd\u6570getmax \u662f\u600e\u6837\u5f00\u59cb\u5b9a\u4e49\u7684\uff1a<\/p>\n\n\n\n

template <class T>
T pair::getmax ()<\/code><\/p>\n\n\n\n

\u6240\u6709\u5199 T \u7684\u5730\u65b9\u90fd\u662f\u5fc5\u9700\u7684\uff0c\u6bcf\u6b21\u4f60\u5b9a\u4e49\u6a21\u677f\u7c7b\u7684\u6210\u5458\u51fd\u6570\u7684\u65f6\u5019\u90fd\u9700\u8981\u9075\u5faa\u7c7b\u4f3c\u7684\u683c\u5f0f\uff08\u8fd9\u91cc\u7b2c\u4e8c\u4e2aT\u8868\u793a\u51fd\u6570\u8fd4\u56de\u503c\u7684\u7c7b\u578b\uff0c\u8fd9\u4e2a\u6839\u636e\u9700\u8981\u53ef\u80fd\u4f1a\u6709\u53d8\u5316\uff09\u3002<\/p>\n\n\n\n

\u6a21\u677f\u7279\u6b8a\u5316(Template specialization)<\/h3>\n\n\n\n

\u6a21\u677f\u7684\u7279\u6b8a\u5316\u662f\u5f53\u6a21\u677f\u4e2d\u7684pattern\u6709\u786e\u5b9a\u7684\u7c7b\u578b\u65f6\uff0c\u6a21\u677f\u6709\u4e00\u4e2a\u5177\u4f53\u7684\u5b9e\u73b0\u3002\u4f8b\u5982\u5047\u8bbe\u6211\u4eec\u7684\u7c7b\u6a21\u677fpair \u5305\u542b\u4e00\u4e2a\u53d6\u6a21\u8ba1\u7b97\uff08module operation\uff09\u7684\u51fd\u6570\uff0c\u800c\u6211\u4eec\u5e0c\u671b\u8fd9\u4e2a\u51fd\u6570\u53ea\u6709\u5f53\u5bf9\u8c61\u4e2d\u5b58\u50a8\u7684\u6570\u636e\u4e3a\u6574\u578b(int)\u7684\u65f6\u5019\u624d\u80fd\u5de5\u4f5c\uff0c\u5176\u4ed6\u65f6\u5019\uff0c\u6211\u4eec\u9700\u8981\u8fd9\u4e2a\u51fd\u6570\u603b\u662f\u8fd4\u56de0\u3002\u8fd9\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u7684\u4ee3\u7801\u6765\u5b9e\u73b0\uff1a<\/p>\n\n\n\n

\/\/ Template specialization#include <iostream.h>template <class T> class pair {    T value1, value2;public:    pair (T first, T second){        value1=first;        value2=second;    }    T module () {return 0;}};template <>class pair <int> {    int value1, value2;public:    pair (int first, int second){        value1=first;        value2=second;    }    int module ();};

template <>int pair<int>::module() {    return value1%value2;}

int main () {    pair <int> myints (100,75);    pair <float> myfloats (100.0,75.0);    cout << myints.module() << ‘\\n’;    cout << myfloats.module() << ‘\\n’;    return 0;}<\/td>		25
0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

\u7531\u4e0a\u9762\u7684\u4ee3\u7801\u53ef\u4ee5\u770b\u5230\uff0c\u6a21\u677f\u7279\u6b8a\u5316\u7531\u4ee5\u4e0b\u683c\u5f0f\u5b9a\u4e49\uff1a<\/p>\n\n\n\n

template <> class class_name <type><\/code><\/p>\n\n\n\n

\u8fd9\u4e2a\u7279\u6b8a\u5316\u672c\u8eab\u4e5f\u662f\u6a21\u677f\u5b9a\u4e49\u7684\u4e00\u90e8\u5206\uff0c\u56e0\u6b64\uff0c\u6211\u4eec\u5fc5\u987b\u5728\u8be5\u5b9a\u4e49\u5f00\u5934\u5199template <>\u3002\u800c\u4e14\u56e0\u4e3a\u5b83\u786e\u5b9e\u4e3a\u4e00\u4e2a\u5177\u4f53\u7c7b\u578b\u7684\u7279\u6b8a\u5b9a\u4e49\uff0c\u901a\u7528\u6570\u636e\u7c7b\u578b\u5728\u8fd9\u91cc\u4e0d\u80fd\u591f\u4f7f\u7528\uff0c\u6240\u4ee5\u7b2c\u4e00\u5bf9\u5c16\u62ec\u53f7<> \u5185\u5fc5\u987b\u4e3a\u7a7a\u3002\u5728\u7c7b\u540d\u79f0\u540e\u9762\uff0c\u6211\u4eec\u5fc5\u987b\u5c06\u8fd9\u4e2a\u7279\u6b8a\u5316\u4e2d\u4f7f\u7528\u7684\u5177\u4f53\u6570\u636e\u7c7b\u578b\u5199\u5728\u5c16\u62ec\u53f7<>\u4e2d\u3002<\/p>\n\n\n\n

\u5f53\u6211\u4eec\u7279\u6b8a\u5316\u6a21\u677f\u7684\u4e00\u4e2a\u6570\u636e\u7c7b\u578b\u7684\u65f6\u5019\uff0c\u540c\u65f6\u8fd8\u5fc5\u987b\u91cd\u65b0\u5b9a\u4e49\u7c7b\u7684\u6240\u6709\u6210\u5458\u7684\u7279\u6b8a\u5316\u5b9e\u73b0\uff08\u5982\u679c\u4f60\u4ed4\u7ec6\u770b\u4e0a\u9762\u7684\u4f8b\u5b50\uff0c\u4f1a\u53d1\u73b0\u6211\u4eec\u4e0d\u5f97\u4e0d\u5728\u7279\u6b8a\u5316\u7684\u5b9a\u4e49\u4e2d\u5305\u542b\u5b83\u81ea\u5df1\u7684\u6784\u9020\u51fd\u6570 constructor\uff0c\u867d\u7136\u5b83\u4e0e\u901a\u7528\u6a21\u677f\u4e2d\u7684\u6784\u9020\u51fd\u6570\u662f\u4e00\u6837\u7684\uff09\u3002\u8fd9\u6837\u505a\u7684\u539f\u56e0\u5c31\u662f\u7279\u6b8a\u5316\u4e0d\u4f1a\u7ee7\u627f\u901a\u7528\u6a21\u677f\u7684\u4efb\u4f55\u4e00\u4e2a\u6210\u5458\u3002<\/p>\n\n\n\n

\u6a21\u677f\u7684\u53c2\u6570\u503c(Parameter values for templates)<\/h3>\n\n\n\n

\u9664\u4e86\u6a21\u677f\u53c2\u6570\u524d\u9762\u8ddf\u5173\u952e\u5b57class \u6216 typename \u8868\u793a\u4e00\u4e2a\u901a\u7528\u7c7b\u578b\u5916\uff0c\u51fd\u6570\u6a21\u677f\u548c\u7c7b\u6a21\u677f\u8fd8\u53ef\u4ee5\u5305\u542b\u5176\u5b83\u4e0d\u662f\u4ee3\u8868\u4e00\u4e2a\u7c7b\u578b\u7684\u53c2\u6570\uff0c\u4f8b\u5982\u4ee3\u8868\u4e00\u4e2a\u5e38\u6570\uff0c\u8fd9\u4e9b\u901a\u5e38\u662f\u57fa\u672c\u6570\u636e\u7c7b\u578b\u7684\u3002\u4f8b\u5982\uff0c\u4e0b\u9762\u7684\u4f8b\u5b50\u5b9a\u4e49\u4e86\u4e00\u4e2a\u7528\u6765\u5b58\u50a8\u6570\u7ec4\u7684\u7c7b\u6a21\u677f\uff1a<\/p>\n\n\n\n

\/\/ array template#include <iostream.h>template <class T, int N>class array {    T memblock [N];public:    void setmember (int x, T value);    T getmember (int x);};template <class T, int N>void array<T,N>::setmember (int x, T value) {    memblock[x]=value;}template <class T, int N>T array<T,N>::getmember (int x) {    return memblock[x];}int main () {    array <int,5> myints;    array <float,5> myfloats;    myints.setmember (0,100);    myfloats.setmember (3,3.1416);    cout << myints.getmember(0) << ‘\\n’;    cout << myfloats.getmember(3) << ‘\\n’;    return 0;}<\/td>100
3.1416<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

\u6211\u4eec\u4e5f\u53ef\u4ee5\u4e3a\u6a21\u677f\u53c2\u6570\u8bbe\u7f6e\u9ed8\u8ba4\u503c\uff0c\u5c31\u50cf\u4e3a\u51fd\u6570\u53c2\u6570\u8bbe\u7f6e\u9ed8\u8ba4\u503c\u4e00\u6837\u3002<\/p>\n\n\n\n

\u4e0b\u9762\u662f\u4e00\u4e9b\u6a21\u677f\u5b9a\u4e49\u7684\u4f8b\u5b50\uff1a<\/p>\n\n\n\n

template <class T> \/\/ \u6700\u5e38\u7528\u7684\uff1a\u4e00\u4e2aclass \u53c2\u6570\u3002<\/p>\n\n\n\n

template <class T, class U> \/\/ \u4e24\u4e2aclass \u53c2\u6570\u3002<\/p>\n\n\n\n

template <class T, int N> \/\/ \u4e00\u4e2aclass \u548c\u4e00\u4e2a\u6574\u6570\u3002<\/p>\n\n\n\n

template <class T = char> \/\/ \u6709\u4e00\u4e2a\u9ed8\u8ba4\u503c\u3002<\/p>\n\n\n\n

template <int Tfunc (int)> \/\/ \u53c2\u6570\u4e3a\u4e00\u4e2a\u51fd\u6570\u3002<\/p>\n\n\n\n

\u6a21\u677f\u4e0e\u591a\u6587\u4ef6\u5de5\u7a0b (Templates and multiple-file projects)<\/h3>\n\n\n\n

\u4ece\u7f16\u8bd1\u5668\u7684\u89d2\u5ea6\u6765\u770b\uff0c\u6a21\u677f\u4e0d\u540c\u4e8e\u4e00\u822c\u7684\u51fd\u6570\u6216\u7c7b\u3002\u5b83\u4eec\u5728\u9700\u8981\u65f6\u624d\u88ab\u7f16\u8bd1(compiled on demand)\uff0c\u4e5f\u5c31\u662f\u8bf4\u4e00\u4e2a\u6a21\u677f\u7684\u4ee3\u7801\u76f4\u5230\u9700\u8981\u751f\u6210\u4e00\u4e2a\u5bf9\u8c61\u7684\u65f6\u5019(instantiation)\u624d\u88ab\u7f16\u8bd1\u3002\u5f53\u9700\u8981instantiation\u7684\u65f6\u5019\uff0c\u7f16\u8bd1\u5668\u6839\u636e\u6a21\u677f\u4e3a\u7279\u5b9a\u7684\u8c03\u7528\u6570\u636e\u7c7b\u578b\u751f\u6210\u4e00\u4e2a\u7279\u6b8a\u7684\u51fd\u6570\u3002<\/p>\n\n\n\n

\u5f53\u5de5\u7a0b\u53d8\u5f97\u8d8a\u6765\u8d8a\u5927\u7684\u65f6\u5019\uff0c\u7a0b\u5e8f\u4ee3\u7801\u901a\u5e38\u4f1a\u88ab\u5206\u5272\u4e3a\u591a\u4e2a\u6e90\u7a0b\u5e8f\u6587\u4ef6\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u901a\u5e38\u63a5\u53e3(interface)\u548c\u5b9e\u73b0(implementation)\u662f\u5206\u5f00\u7684\u3002\u7528\u4e00\u4e2a\u51fd\u6570\u5e93\u505a\u4f8b\u5b50\uff0c\u63a5\u53e3\u901a\u5e38\u5305\u62ec\u6240\u6709\u80fd\u88ab\u8c03\u7528\u7684\u51fd\u6570\u7684\u539f\u578b\u5b9a\u4e49\u3002\u5b83\u4eec\u901a\u5e38\u88ab\u5b9a\u4e49\u5728\u4ee5.h \u4e3a\u6269\u5c55\u540d\u7684\u5934\u6587\u4ef6 (header file) \u4e2d\uff1b\u800c\u5b9e\u73b0 (\u51fd\u6570\u7684\u5b9a\u4e49) \u5219\u5728\u72ec\u7acb\u7684C++\u4ee3\u7801\u6587\u4ef6\u4e2d\u3002<\/p>\n\n\n\n

\u6a21\u677f\u8fd9\u79cd\u7c7b\u4f3c\u5b8f(macro-like) \u7684\u529f\u80fd\uff0c\u5bf9\u591a\u6587\u4ef6\u5de5\u7a0b\u6709\u4e00\u5b9a\u7684\u9650\u5236\uff1a\u51fd\u6570\u6216\u7c7b\u6a21\u677f\u7684\u5b9e\u73b0 (\u5b9a\u4e49) \u5fc5\u987b\u4e0e\u539f\u578b\u58f0\u660e\u5728\u540c\u4e00\u4e2a\u6587\u4ef6\u4e2d\u3002\u4e5f\u5c31\u662f\u8bf4\u6211\u4eec\u4e0d\u80fd\u518d \u5c06\u63a5\u53e3(interface)\u5b58\u50a8\u5728\u5355\u72ec\u7684\u5934\u6587\u4ef6\u4e2d\uff0c\u800c\u5fc5\u987b\u5c06\u63a5\u53e3\u548c\u5b9e\u73b0\u653e\u5728\u4f7f\u7528\u6a21\u677f\u7684\u540c\u4e00\u4e2a\u6587\u4ef6\u4e2d\u3002<\/p>\n\n\n\n

\u56de\u5230\u51fd\u6570\u5e93\u7684\u4f8b\u5b50\uff0c\u5982\u679c\u6211\u4eec\u60f3\u8981\u5efa\u7acb\u4e00\u4e2a\u51fd\u6570\u6a21\u677f\u7684\u5e93\uff0c\u6211\u4eec\u4e0d\u80fd\u518d\u4f7f\u7528\u5934\u6587\u4ef6(.h) \uff0c\u53d6\u800c\u4ee3\u4e4b\uff0c\u6211\u4eec\u5e94\u8be5\u751f\u6210\u4e00\u4e2a\u6a21\u677f\u6587\u4ef6(template file)\uff0c\u5c06\u51fd\u6570\u6a21\u677f\u7684\u63a5\u53e3\u548c\u5b9e\u73b0 \u90fd\u653e\u5728\u8fd9\u4e2a\u6587\u4ef6\u4e2d (\u8fd9\u79cd\u6587\u4ef6\u6ca1\u6709\u60ef\u7528\u6269\u5c55\u540d\uff0c\u9664\u4e86\u4e0d\u8981\u4f7f\u7528.h\u6269\u5c55\u540d\u6216\u4e0d\u8981\u4e0d\u52a0\u4efb\u4f55\u6269\u5c55\u540d)\u3002\u5728\u4e00\u4e2a\u5de5\u7a0b\u4e2d\u591a\u6b21\u5305\u542b\u540c\u65f6\u5177\u6709\u58f0\u660e\u548c\u5b9e\u73b0\u7684\u6a21\u677f\u6587\u4ef6\u5e76\u4e0d\u4f1a\u4ea7\u751f\u94fe\u63a5\u9519\u8bef (linkage errors)\uff0c\u56e0\u4e3a\u5b83\u4eec\u53ea\u6709\u5728\u9700\u8981\u65f6\u624d\u88ab\u7f16\u8bd1\uff0c\u800c\u517c\u5bb9\u6a21\u677f\u7684\u7f16\u8bd1\u5668\u5e94\u8be5\u5df2\u7ecf\u8003\u8651\u5230\u8fd9\u79cd\u60c5\u51b5\uff0c\u4e0d\u4f1a\u751f\u6210\u91cd\u590d\u7684\u4ee3\u7801\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

5.1 \u6a21\u677f(Templates) \u6a21\u677f(Templates)\u662fANSI-C++ \u6807\u51c6\u4e2d\u65b0\u5f15\u5165\u7684\u6982\u5ff5\u3002\u5982\u679c\u4f60\u4f7f\u7528\u7684 C++ \u7f16\u8bd1\u5668\u4e0d\u7b26\u5408\u8fd9\u4e2a\u6807\u51c6\uff0c\u5219\u4f60\u5f88\u53ef\u80fd\u4e0d\u80fd\u4f7f\u7528\u6a21\u677f\u3002 \u51fd\u6570\u6a21\u677f( Function templates) \u6a21\u677f(Templates)\u4f7f\u5f97\u6211\u4eec\u53ef\u4ee5\u751f\u6210\u901a\u7528\u7684\u51fd\u6570\uff0c\u8fd9\u4e9b\u51fd\u6570\u80fd\u591f\u63a5\u53d7\u4efb\u610f\u6570\u636e\u7c7b\u578b\u7684\u53c2\u6570\uff0c\u53ef\u8fd4\u56de\u4efb\u610f\u7c7b\u578b\u7684\u503c\uff0c\u800c\u4e0d\u9700\u8981\u5bf9\u6240\u6709\u53ef\u80fd\u7684\u6570\u636e\u7c7b\u578b\u8fdb\u884c\u51fd\u6570\u91cd\u8f7d\u3002\u8fd9\u5728\u4e00\u5b9a\u7a0b\u5ea6\u4e0a\u5b9e\u73b0\u4e86\u5b8f\uff08macro\uff09\u7684\u4f5c\u7528\u3002\u5b83\u4eec\u7684\u539f\u578b\u5b9a\u4e49\u53ef\u4ee5\u662f\u4e0b\u9762\u4e24\u79cd\u4e2d\u7684\u4efb\u4f55\u4e00\u4e2a\uff1a template <class identifier> function_declaration;template <typename identifier> function_declaration; \u4e0a\u9762\u4e24\u79cd\u539f\u578b\u5b9a\u4e49\u7684\u4e0d\u540c\u4e4b\u5904\u5728\u5173\u952e\u5b57class \u6216 typename\u7684\u4f7f\u7528\u3002\u5b83\u4eec\u5b9e\u9645\u662f\u5b8c\u5168\u7b49\u4ef7\u7684\uff0c\u56e0\u4e3a\u4e24\u79cd\u8868\u8fbe\u7684\u610f\u601d\u548c\u6267\u884c\u90fd\u4e00\u6a21\u4e00\u6837\u3002 \u4f8b\u5982\uff0c\u8981\u751f\u6210\u4e00\u4e2a\u6a21\u677f\uff0c\u8fd4\u56de\u4e24\u4e2a\u5bf9\u8c61\u4e2d\u8f83\u5927\u7684\u4e00\u4e2a\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u5199\uff1a template <class GenericType> GenericType GetMax (GenericType a, GenericType b) { return (a>b?a:b); } \u5728\u7b2c\u4e00\u884c\u58f0\u660e\u4e2d\uff0c\u6211\u4eec\u5df2\u7ecf\u751f\u6210\u4e86\u4e00\u4e2a\u901a\u7528\u6570\u636e\u7c7b\u578b\u7684\u6a21\u677f\uff0c\u53eb\u505aGenericType\u3002\u56e0\u6b64\u5728\u5176\u540e\u9762\u7684\u51fd\u6570\u4e2d\uff0cGenericType \u6210\u4e3a\u4e00\u4e2a\u6709\u6548\u7684\u6570\u636e\u7c7b\u578b\uff0c\u5b83\u88ab\u7528\u6765\u5b9a\u4e49\u4e86\u4e24\u4e2a\u53c2\u6570a\u548c b \uff0c\u5e76\u88ab\u7528\u4f5c\u4e86\u51fd\u6570GetMax\u7684\u8fd4\u56de\u503c\u7c7b\u578b\u3002 GenericType \u4ecd\u6ca1\u6709\u4ee3\u8868\u4efb\u4f55\u5177\u4f53\u7684\u6570\u636e\u7c7b\u578b\uff1b\u5f53\u51fd\u6570 GetMax \u88ab\u8c03\u7528\u7684\u65f6\u5019\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u4efb\u4f55\u6709\u6548\u7684\u6570\u636e\u7c7b\u578b\u6765\u8c03\u7528\u5b83\u3002\u8fd9\u4e2a\u6570\u636e\u7c7b\u578b\u5c06\u88ab\u4f5c\u4e3apattern\u6765\u4ee3\u66ff\u51fd\u6570\u4e2dGenericType \u51fa\u73b0\u7684\u5730\u65b9\u3002\u7528\u4e00\u4e2a\u7c7b\u578bpattern\u6765\u8c03\u7528\u4e00\u4e2a\u6a21\u677f\u7684\u65b9\u6cd5\u5982\u4e0b\uff1a function <type> (parameters); \u4f8b\u5982\uff0c\u8981\u8c03\u7528GetMax \u6765\u6bd4\u8f83\u4e24\u4e2aint\u7c7b\u578b\u7684\u6574\u6570\u53ef\u4ee5\u8fd9\u6837\u5199\uff1a int x,y;GetMax <int> (x,y); \u56e0\u6b64\uff0cGetMax \u7684\u8c03\u7528\u5c31\u597d\u50cf\u6240\u6709\u7684GenericType \u51fa\u73b0\u7684\u5730\u65b9\u90fd\u7528int \u6765\u4ee3\u66ff\u4e00\u6837\u3002 \u8fd9\u91cc\u662f\u4e00\u4e2a\u4f8b\u5b50\uff1a \/\/ function […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":361,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/pages\/365"}],"collection":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/types\/page"}],"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=365"}],"version-history":[{"count":1,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/pages\/365\/revisions"}],"predecessor-version":[{"id":366,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/pages\/365\/revisions\/366"}],"up":[{"embeddable":true,"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/pages\/361"}],"wp:attachment":[{"href":"https:\/\/www.prglab.com\/blog\/wp-json\/wp\/v2\/media?parent=365"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}