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#include <iostream>

class CVirtual {

public:

//virtual void show_something() = 0;

/*virtual*/ void show_something() {

std::cout << "CVirtual" << std::endl;

}

};

class CInstance: public CVirtual {

public:

explicit CInstance(int var): var(var) {}

virtual void show_something();

int var;

};

void CInstance::show_something()

{

std::cout << "CInstance variable: " << var << std::endl;

}

class CIns: public CInstance {

public:

explicit CIns(int test): CInstance(233), test(test) {}

virtual void show_something();

int test;

};

void CIns::show_something()

{

std::cout << "CIns variable: " << test << std::endl;

}

/*

虚函数的作用是实现多态性，即将子类实例指针赋值给父类

父类调用同名函数时，执行的是子类中的实现

而纯虚数除了上述功能外，就是约束子类必须实现父类函数才可实例化

即起到预留接口的作用

而非虚函数父类调用同名函数时，执行自己的实现

*/

int main(int argc, char **argv)

{

CVirtual *cvirtual = new CInstance(20);

cvirtual->show_something();

CInstance *cinstance = new CIns(666);

cinstance->show_something();

return 0;

}