类继承时访问标识的作用域

class Base{
public:
	int Base_public;
protected:
	int Base_protected;
private:
	int Base_private;
};
class Derived:public Base{
public:
	int Derived_public;
protected:
	int Derived_protected;
private:
	int Derived_private;
public:
	void Check();
	void Check(Base& vBase,Derived& vDerived);
};
void Derived::Check()
{
	//this 是Derived类型的，在this所属类作用域(Derived作用域)里

	//，Derived本身定义的变量，无论什么访问标号都可以
	Derived_private =5;  //ok
	Derived_protected=5; //ok
	Derived_public = 5; //ok
	//Derived继承Base来的变量，可以访问Base中public和protected标号的成员变量
	Base_public =5;//ok
	Base_protected =5;//ok
	//Base_private =5;//error

	//给每个变量前加上this指针，更方便理解
	//类类型变量在所属类作用域里，变量中由所属类自身定义的成员变量可以任意访问
						//所属类继承来的变量，只可以访问public和protected成员变量
	//类类型变量在其他作用域里，只能访问public成员变量
}
//
void Derived::Check(Base &vBase,Derived &vDerivde)
{
	//vBase是Base类型，在Derived类作用域里（非本身作用域）,只能访问public标示的成员变量
	//vBase.Base_private =5;//error
	//vBase.Base_protected =5;//error
	vBase.Base_public =5;//ok

	//vDerived是Derived类型，在Derived作用域里（本身作用域）,所属类定义的变量，可任意访问
	vDerivde.Derived_public =5;//ok
	vDerivde.Derived_protected =5;//ok
	vDerivde.Derived_private =5;//ok
					//所属类继承来的变量，只能访问public,protected
	//vDerivde.Base_private =5;//error
	vDerivde.Base_protected =5;//ok
	vDerivde.Base_public =5;//ok

	//private任何时候只能在本身作用域使用

}

　　

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