26.虚函数示例理解
Eg1.都没虚函数
#include<iostream>
usingnamespace std;
class Father{
public:
Father(){
cout <<"this is the Father constructor!"<< endl;
}
void watchTv(){
cout <<"Father is watching tv!"<< endl;
}
void say(){
cout <<"Father is saying!"<< endl;
}
};
class Son :public Father{
public:
Son(){
cout <<"this is the Son constructor!"<< endl;
}
void watchTv(){
cout <<"Son is watching tv!"<< endl;
}
void say(){
cout <<"Son is saying!"<< endl;
}
};
int main(){
Father* fa = new Son();
fa->watchTv();
fa->say();
system("pause");
return 0;
}
运行结果
解析：因为是Father类型的指针直接调用Father类函数
Eg2.子类有虚函数
#include<iostream>
usingnamespace std;
class Father{
public:
Father(){
cout <<"this is the Father constructor!"<< endl;
}
void watchTv(){
cout <<"Father is watching tv!"<< endl;
}
void say(){
cout <<"Father is saying!"<< endl;
}
};
class Son :public Father{
public:
Son(){
cout <<"this is the Son constructor!"<< endl;
}
void watchTv(){
cout <<"Son is watching tv!"<< endl;
}
virtualvoid say(){
cout <<"Son is saying!"<< endl;
}
};
int main(){
Father* fa = new Son();
fa->watchTv();
fa->say();
system("pause");
return 0;
}
运行结果：
解析：也是直接调用父类函数
Eg3.子类有虚函数
#include<iostream>
usingnamespace std;
class Father{
public:
Father(){
cout <<"this is the Father constructor!"<< endl;
}
void watchTv(){
cout <<"Father is watching tv!"<< endl;
}
virtualvoid say(){
cout <<"Father is saying!"<< endl;
}
};
class Son :public Father{
public:
Son(){
cout <<"this is the Son constructor!"<< endl;
}
void watchTv(){
cout <<"Son is watching tv!"<< endl;
}
void say(){
cout <<"Son is saying!"<< endl;
}
};
int main(){
Father* fa = new Son();
fa->watchTv();
fa->say();
system("pause");
return 0;
}
运行结果
解析：Father* fa = new Son()表示在son上Father类型指针，父类有虚函数，就会产生一个虚表，指向该函数，子数也会产生同样一个虚表，不过是指向父类，当主函数执行到fa->say();同于子类重写，父类也跟着重写了，所以是
。
Eg4.子类有虚函数
#include<iostream>
usingnamespace std;
class Father{
public:
Father(){
cout <<"this is the Father constructor!"<< endl;
}
void watchTv(){
cout <<"Father is watching tv!"<< endl;
}
virtualvoid say(){
cout <<"Father is saying!"<< endl;
}
};
class Son :public Father{
public:
Son(){
cout <<"this is the Son constructor!"<< endl;
}
void watchTv(){
cout <<"Son is watching tv!"<< endl;
}
virtualvoid say(){
cout <<"Son is saying!"<< endl;
}
};
int main(){
Father* fa = new Son();
fa->watchTv();
fa->say();
system("pause");
return 0;
}
运行结果：
解析：
同eg3一样
全总结：父类和了类，一般都是先运行父类再运行子数，虚函数只改写子类。
