派生类实现具有公共函数签名的多个接口 [英] Derived class implementing multiple interfaces with a common function signature

问题描述

当我尝试编译我的代码时，我收到一个编译错误。
错误是：

I'm getting a compile error when I try to compile my code. The error is this:

multi.cc: In function ‘int main()’:
multi.cc:35: error: cannot declare variable ‘mdc’ to be of abstract type ‘MostDerivedClass’
multi.cc:27: note:   because the following virtual functions are pure within ‘MostDerivedClass’:
multi.cc:13: note:  virtual int Interface2::common_func()
multi.cc:36: error: request for member ‘common_func’ is ambiguous
multi.cc:13: error: candidates are: virtual int Interface2::common_func()
multi.cc:21: error:                 virtual int InterimClass::common_func()

这里是我的代码：

class Interface1 {
public:
    virtual int common_func() = 0;
    virtual ~Interface1() {};
};

class Interface2 {
public:
    virtual int common_func() = 0;
    virtual int new_func() = 0;
    virtual ~Interface2() {};
};


class InterimClass : public Interface1 {
public:
    virtual int common_func() {
        return 10;
    }
};


class MostDerivedClass : public InterimClass, public Interface2 {
public:
    virtual int new_func() {
        return 20;
    }   
};

int main() {
    MostDerivedClass mdc;
    int x = mdc.common_func();
    cout << "The value = " << x << endl;    

    Interface2 &subset_of_funcs = dynamic_cast<Interface2 &>(mdc);
    x = subset_of_funcs.common_func();
}

我的问题：

• 我如何告诉编译器common_func（）已经由InterimClass实现，它是MostDerivedClass的基类？

• How do I tell the compiler that common_func() is already implemented by the InterimClass which is a base class of MostDerivedClass?

有另一种方法来解决我的问题吗？我真正想做的是能够从Interface2调用common_func。我正在使用一些遗留代码与大量的方法在Interface1。在我的新代码中，我只想调用这些Interface1函数的一小部分，再加上我需要添加的几个。

Is there another way to fix my problem? What I would really like to do is to be able to also call common_func from Interface2. I'm working with some legacy code with a huge amount of methods in Interface1. In my new code, I only want to call a small set of these Interface1 functions, plus a few that I need to add.

推荐答案

您需要在 MostDerivedClass common_func（） >以满足您从 Interface2

You need to define a common_func() anyway in MostDerivedClass to satisfy your inheritance from Interface2

的继承，您可以尝试类似

you can try something like

virtual int common_func() {
    return InterimClass::common_func();
}

如果您不能更改第一个 Interface1

如果你想在你的类之间有一个真正的继承关系，你需要遵循Lol4t0建议。从 Interface1 中提取超类，并创建此新创建的类的 Interface2 子类。示例：

If you want a real inheritance relationship between your classes you need to follow Lol4t0 advice. Extract a superclass from Interface1, and make Interface2 subclass of this newly created class. Example :

class RootInterface{
public :
    virtual int common_func() = 0;
    virtual ~RootInterface(){}
};

class Interface1 : public virtual RootInterface{
public:
    virtual ~Interface1() {};
};

class Interface2 : public virtual RootInterface{
    public:
    virtual int new_func() = 0;
    virtual ~Interface2() {};
};

class InterimClass : public Interface1 {
    public:
    virtual int common_func() {
        return 10;
    }
};

class MostDerivedClass : public InterimClass, public Interface2 {
public:
    virtual int new_func() {
        return 20;
    }
};

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