奇怪的循環模板patterm：雙遺產

Question

我有以下幾點：

class Base 
{ 
protected: 
    std::string _name; 

public: 
    virtual ~Base(){} 

    const std::string &name; 

    Base() 
     : _name ("(no name)") 
     , name(_name) 
    {} 
}; 

template <typename T> 
class BaseH : public Base 
{ 
public: 
    virtual ~BaseH() {} 
    BaseH() : Base() {} 

    T& operator~(){ ; return static_cast<T&>(*this);} 
}; 

class One : public BaseH<One> 
{ 
public: 
    One() : BaseH<One>() { _name = "One"; } 

}; 

class Two 
    : public One 
    , public BaseH<Two> 
{ 
public: 
    Two() : BaseH<Two>() { _name = "Two"; } 

}; 


int main(int argc, char *argv[]) 
{ 
    std::cout << Two().name << std::endl; 

    return 0; 
} 

我希望得到來自One和BaseH<Two>Two，因爲Two是One專業化和operator~在BaseH必須始終返回調用它的對象的類型的引用。

編譯錯誤是明顯的：

In constructor ‘Two::Two()’: 
    error: reference to ‘_name’ is ambiguous 
    error: candidates are: std::string Base::_name 
    error:     std::string Base::_name 
In function ‘int main(int, char**)’: 
    error: request for member ‘name’ is ambiguous 
    error: candidates are: const string& Base::name 
    error:     const string& Base::name 

如何使_name和兩個One和Twoname訪問，同時設定通過構造代表團const參考？最乾淨的方法是什麼？

Answer 1

看起來像你有diamond problem。你有沒有試過virtual inheritance？

如：

template <typename T> 
class BaseH : virtual public Base 
{ 
    // ... 
}; 

class One : virtual public BaseH<One> 
{ 
    // ... 
}; 

編輯：對鑽石的問題在這裏進一步閱讀：http://www.cprogramming.com/tutorial/virtual_inheritance.html