C++中繼承的可見性分析

這次主要搞清了類的成員和繼承方式中的protected屬性。簡單說，它對內可見，對外私有。與private屬性不同的是，對於父類中的protected成員，繼承後在子類中依然可見。如果上述繼承以private方式進行，protected成員在繼承後會成爲private成員。

 

//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;
}