C++中继承的可见性分析

这次主要搞清了类的成员和继承方式中的protected属性。简单说，它对内可见，对外私有。与private属性不同的是，对于父类中的protected成员，继承后在子类中依然可见。如果上述继承以private方式进行，protected成员在继承后会成为private成员。

 

// Inherency.cpp
// demo of the inherency property in C++

#include  < iostream.h >

class  Base
... {
private:
    char *pv;

protected:
    char *pt;

public:
    char *pb;
    Base()
    ...{
        this->pv = "private";
        this->pt = "protected";
        this->pb = "public";
    }
} ;

class  Pv_Base: private  Base 
... {
public:
    void show()
    ...{
        //cout<<this->pv<<" in Pv_Base.show()"<<endl; //error
        cout<<this->pt<<" in Pv_Base.show()"<<endl;
        cout<<this->pb<<" in Pv_Base.show()"<<endl;
    }
} ;

class  Pt_Base: protected  Base
... {
public:
    void show()
    ...{
        //cout<<this->pv<<" in Pt_Base.show()"<<endl; //error
        cout<<this->pt<<" in Pt_Base.show()"<<endl;
        cout<<this->pb<<" in Pt_Base.show()"<<endl;
    }
} ;

class  Pb_Base: public  Base
... {
public:
    void show()
    ...{
        //cout<<this->pv<<" in Pb_Base.show()"<<endl; //error
        cout<<this->pt<<" in Pb_Base.show()"<<endl;
        cout<<this->pb<<" in Pb_Base.show()"<<endl;
    }
} ;

void  main()
... {
    Base base;
    //cout<<base.pv<<" in main()"<<endl; //error
    //cout<<base.pt<<" in main()"<<endl; //error
    cout<<base.pb<<" in main()"<<endl;
    cout<<endl;

    Pv_Base pv_base;
    //cout<<pv_base.pv<<" in main()"<<endl; //error
    //cout<<pv_base.pt<<" in main()"<<endl; //error
    //cout<<pv_base.pb<<" in main()"<<endl; //error
    pv_base.show();
    cout<<endl;

    Pt_Base pt_base;
    //cout<<pt_base.pv<<" in main()"<<endl; //error
    //cout<<pt_base.pt<<" in main()"<<endl; //error
    //cout<<pt_base.pb<<" in main()"<<endl; //error
    pt_base.show();
    cout<<endl;

    Pb_Base pb_base;
    //cout<<pb_base.pv<<" in main()"<<endl; //error
    //cout<<pb_base.pt<<" in main()"<<endl; //error
    cout<<pb_base.pb<<" in main()"<<endl;
    pb_base.show();
    cout<<endl;
}