浅谈C++继承方式

简单地说下C++类的3种继承方式，分别是public继承，protected继承，private继承。

最常用的还是public继承。class默认的是private继承，它的member如果没写权限也是默认

private。struct则相反，默认的是public继承。结合下面的图示和代码，对C++的继承就有了

比较清晰的认识了。

继承之后，derived class 继承过后的member的属性就是图中所示。

代码主要从：

1.基类成员对其对象的可见性：  

2. 基类成员对派生类的可见性：  

3. 基类成员对派生类对象的可见性：

这3个方面谈的。

#include <iostream>

class base{
public:
	base(){
		a = 0;
		b = 1;
		c = 2;
	}
	int a;
protected:
	int b;
private:
	int c;
};

class derived1 : public base{//public继承
public:
	void fun(){//derived class可以访问public和protected member
		std::cout<<base::a<<base::b<<std::endl;
	//	std::cout<<base::c;//不能访问
	}
};
class derived2 : protected base{//protected继承
public:
	void fun(){//derived class可以访问public和protected member
		std::cout<<base::a<<base::b<<std::endl;
	 // std::cout<<base::c;//不能访问
	}
};
class derived3 : private base{//private继承
public:
	void fun(){//derived class可以访问public和protected member
		std::cout<<base::a<<base::b<<std::endl;
	 // std::cout<<base::c;//不能访问
	}
};
class derived4 : public derived3{//base的member不能被private继承的派生类的子类访问
public:
	void fun(){
	//	std::cout<<a;
	}
};
class derived5 : base{//默认private继承
	void fun(){//derived class可以访问public和protected member
		std::cout<<base::a<<base::b;
		// std::cout<<base::c;//不能访问
	}	
};
int main(void)
{
	base b1;
	derived1 d1;
	derived2 d2;
	derived3 d3;
	d1.fun();
	d2.fun();
	d3.fun();
	std::cout<<b1.a;//base class Object只能访问public member
	std::cout<<d1.a;//public继承时 derived class Object只能访问base class的public member
	//std::cout<<d1.b<<d1.c;//不能访问
	//std::cout<<d2.a<<d2.b;//protected继承时 derived class Object不能问访base class的member
	//std::cout<<d3.a;//private继承时 derived class Object不能问访base class的member
	return 0;
}