在 C++ 中构建简单函数以继承 3 类

Question

我创造了 3 个 classes - 祖母、母亲和女儿。我写了一段代码，使女儿 class 继承自母亲 class，而母亲 class 继承自祖母 calss。

GrandMother.h :-

#ifndef GRANDMOTHER_H
#define GRANDMOTHER_H


class GrandMother
{
    public:
        GrandMother();
        ~GrandMother();
};

#endif // GRANDMOTHER_H

Mother.h :-

#ifndef MOTHER_H
#define MOTHER_H


class Mother: public GrandMother
{
    public:
        Mother();
        ~Mother();
};

#endif // MOTHER_H

Daughter.h :-

#ifndef DAUGHTER_H
#define DAUGHTER_H


class Daughter: public Mother
{
    public:
        Daughter();
        ~Daughter();
};

#endif // DAUGHTER_H

GrandMother.cpp :-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

GrandMother::GrandMother()
{
    cout << "Grand Mother Constructor!!" << endl;
}

GrandMother::~GrandMother()
{
    cout << "Grand Mother Deconstroctor" << endl;
}

Mother.cpp :-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

Mother::Mother()
{
    cout << "Mother Constructor!!" << endl;
}

Mother::~Mother()
{
    cout << "Mother Deconstroctor" << endl;
}

Daughter.cpp:-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

Daughter::Daughter()
{
    cout << "Daughter Constructor!!" << endl;
}

Daughter::~Daughter()
{
    cout << "Daughter Deconstroctor" << endl;
}

main.cpp :-

#include<iostream>
#include "Mother.h"
#include "Daughter.h"
#include "GrandMother.h"
using namespace std;

int main(){
    //GrandMother granny;

    //Mother mom;

    Daughter baby;
}

当我运行代码时，它给了我以下错误：- error: expected class-name before '{' token

任何人都可以告诉我我的代码的哪一部分是错误的。

Answer 1

您的 header 不是 self-contained，因此您必须按正确的顺序包含它们：

#include "GrandMother.h"
#include "Mother.h"
#include "Daughter.h"

但它很脆弱。

正确的方法是使 header 自包含：

#ifndef GRANDMOTHER_H
#define GRANDMOTHER_H

class GrandMother
{
public:
    GrandMother();
    ~GrandMother();
};

#endif // GRANDMOTHER_H

#ifndef MOTHER_H
#define MOTHER_H

#include "GrandMother.h"

class Mother: public GrandMother
{
public:
    Mother();
    ~Mother();
};

#endif // MOTHER_H

#ifndef DAUGHTER_H
#define DAUGHTER_H

#include "Mother.h"

class Daughter: public Mother
{
public:
    Daughter();
    ~Daughter();
};

#endif // DAUGHTER_H

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