c++的模板继承

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       作者：清林，博客名：飞空静渡

 

我们有这么一组这样的类，其类继承关系如下图：

我们先把base, man, 和woman的类写出来，test.h文件

#ifndef TEST_H#define TEST_H #include <iostream>using namespace std;class base {public:base (int id, bool bman):id_(id), bMan(bman){cout<<"base function!"<<endl;}virtual ~base (){}bool sexMan() { return bMan;}protected:int id_;bool bMan; // false is woman, true :is man};class man :public base{public:man (int id):base(id, true){cout<<"I'am a man, id is "<<id_<<endl;}protected:};class woman : public base{public:woman (int id): base(id, false){cout<<"I'am a woman, id is "<<id_<<endl;}protected:};#endif

 

如果我们要写一个男教师的类manTeacher的话就得从man上继承，同理womanTeacher就得从woman上继承，这样我们就得写下两个类了，但这里我们可以通过模板来简化类的写，如下（在test.h文件下面添加）：

 

template<class T> class teacher : public T {public:teacher(int id):T(id){}void say(){if (sexMan())cout<<"I'am a man teacher!"<<endl;elsecout<<"I'am a woman teacher!"<<endl;}private:/* data */};

 

我们测试一下，新建一个cpp文件，main.cpp

#include <vector>#include "test.h"int main(int argc, char *argv[]){teacher<man> t1(5);t1.say();}

 

在vc上可以直接编译，在g++上，要添加-fpermissive，添加这个可以让模板代码由出错降为警告，从而编译通过，vc可以直接编译通过。

编译：

g++ -g -Wall -fpermissive main.cpp

运行： ./a.out
base function!
I'am a man, id is 5
I'am a man teacher!

 

我们再次修改如下：

#include <vector>#include "test.h"int main(int argc, char *argv[]){base* b = new teacher<man>(3);teacher<man> *t = (teacher<man> *)b;t->say();return 0;}

 

编译输出：./a.out
base function!
I'am a man, id is 3
I'am a man teacher

 

再次修改main.cpp

#include <vector>#include "test.h"int main(int argc, char *argv[]){std::vector<base*> vb;base* b1 = new teacher<man>(3);base* b2 = new teacher<woman>(5);vb.push_back(b1);vb.push_back(b2);for(std::vector<base*>::iterator it = vb.begin();it != vb.end();++it){if ((*it)->sexMan()){teacher<man> *t = (teacher<man> *) (*it);t->say();}else{teacher<woman> *t = (teacher<woman> *) (*it);t->say();}}return 0;}

 

编译输出：./a.out
base function!
I'am a man, id is 3
base function!
I'am a woman, id is 5
I'am a man teacher!
I'am a woman teacher!