多重继承的注意点

1, 钻石型多重继承如果不想要底部的类有重复的变量，则需要声明为virtual继承

　　class File{...};

　　class InputFile: virtual public File{..};

　　class OutputFile: virtual public File{....};

　　class IOFile: public InputFile,

　　　　　　　　public OutputFile

　　{...};

2, 多重继承来的成员函数指向一边的指针不能访问另一边的函数

///////////////////////////////////////////////////////////////////////////////
//
//  FileName    :   multi_inherit.h
//  Version     :   0.10    created    2013/11/08 00:00:00
//  Author      :   Jimmy Han
//  Comment     :
//
///////////////////////////////////////////////////////////////////////////////
#ifndef MULTI_INHERIT_H
#define    MULTI_INHERIT_H

class base1{
public:
    void baseFunc();
private:
    int baseElem;
};

class derive1 : public base1 {
public:
    void derive1Func();
private:
    int derive1Elem;
};

class base2{
public:
    void baseFunc();
private:
    int baseElem;
};

class derive2 : public derive1, public base2{
public:
    void derive2Func();

    //to avoid ambigous
    void baseFunc();

private:
    int derive2Elem;
};

#endif

///////////////////////////////////////////////////////////////////////////////
//
//  FileName    :   multi_inherit.cpp
//  Version     :   0.10
//  Author      :   Ryan Han
//  Date        :   2013/07/26 16:50:14
//  Comment     :
//
///////////////////////////////////////////////////////////////////////////////
#include "multi_inherit.h"

#include <iostream>
using namespace std;

void base1::baseFunc() {
    cout << "base1Func was called. " << endl;
}

void base2::baseFunc() {
    cout << "base2Func was called. " << endl;
}

void derive1::derive1Func() {
    cout << "derive1Func was called. " << endl;
}

void derive2::derive2Func() {
    cout << "derive2Func was called. " << endl;
}

void derive2::baseFunc() {
    base2::baseFunc();
}

///////////////////////////////////////////////////////////////////////////////
//
//  FileName    :   multi_inherit_client.cpp
//  Version     :   0.10
//  Author      :   Ryan Han
//  Date        :   2013/07/26 16:50:14
//  Comment     :
//    Output        :
//    $ ./a
// $ ./a.exe
// base2Func was called.
// derive1Func was called.
// derive2Func was called.
// base1Func was called.
// derive1Func was called.

///////////////////////////////////////////////////////////////////////////////
#include "multi_inherit.h"
#include <iostream>
using namespace std;

int main() {
    derive2 d2;
    //if not embed, this will be ambigous and compile error
    d2.baseFunc();
    //could call both derive1Func and derive2Func
    d2.derive1Func();
    d2.derive2Func();

    derive1* b1 = new derive2;
    //call base1 or derive1 functions, OK
    b1->baseFunc();
    b1->derive1Func();
    //call base2 or derive2 functions, compile error.
    //b1->derive2Func();

    return 0;
}

多重继承的注意点