多重继承的不确定基 [英] Ambiguous base with multiple inheritance

问题描述

我试图在一个大的库中写一些类的子类。我得到一个含糊的基地错误。这是一个可编译的问题的例子：

  #include< iostream> 
 
 //我不能改变这些，因为它们在库中：
 class InteractorStyle {}; 
类InteractorStyleCamera：public InteractorStyle {}; 
类InteractorStyleImage：public InteractorStyle {}; 
 
 //这是我的子类（所以我可以改变它们）：
 class PointSelector：public InteractorStyle {}; 
 class PointSelector2D：public InteractorStyleCamera，public PointSelector 
 {
 //此函数必须完全如下所示（库的要求）：
 static PointSelector2D * SafeDownCast（InteractorStyle * o）
 {
 return static_cast< PointSelector2D *>（o）; 
} 
}; 
 
 
 int main（）
 {
 
 return 0; 
} 
  

错误是

< blockquote>

错误：'InteractorStyle'是'PointSelector2D'的不明确的基础。

你的问题是Interactor风格被继承了两次 - 一次是PointSelector2D，一次是InteractorStyleCamera。

查看：

如何避免如果我使用多重继承，C ++中的死亡钻石？

尝试虚拟继承。

I am trying to write some subclasses of classes in a big library. I am getting an "ambiguous base" error. Here is a compilable example of the problem:

#include <iostream>

// I can't change these because they are in the library:
class InteractorStyle {};
class InteractorStyleCamera : public InteractorStyle {};
class InteractorStyleImage : public InteractorStyle {};

// These are my subclasses (so I can change them):
class PointSelector : public InteractorStyle {};
class PointSelector2D : public InteractorStyleCamera, public PointSelector
{
  // This function has to exist exactly like this (a requirement of the library):
  static PointSelector2D* SafeDownCast(InteractorStyle *o)
  {
    return static_cast<PointSelector2D *>(o);
  } 
};


int main()
{

  return 0;
}

The error is

error: ‘InteractorStyle’ is an ambiguous base of ‘PointSelector2D’.

Is there anything I can do in this case?

解决方案

Your problem is that Interactor style is inherited twice - once by PointSelector2D and once by InteractorStyleCamera. This means that you have 2 versions of every member of it contained within your class.

Check out:

How can avoid the Diamond of Death in C++ if I use multiple inheritance?

And try virtual inheritance.

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