遍历 C++ 中不同类型的集合 [英] Iterating through collection of different types in C++

问题描述

情况

我有一个模板类 TIppImage 用于 T 类型的图像.我有单例类 CIppMemoryManager，它可以存储许多不同大小和类型的图像.

I have a template class TIppImage<T> for image of type T. I have singleton class CIppMemoryManager which can store a number of images of different size and type.

class CIppMemoryManager
{
public:
  /// ... Singleton interface ... 

  template<class T> TIppImage<T>* GetImage(width, height);

private:
  CIppMemoryManager();
  ~CIppMemoryManager();

  std::map<IppDataType, void*> m_Containers;
};

IppDataType 是枚举，其值对应于实际类型.所有管理都在模板类 TIppImageContainer 中完成.并且此类的所有特化都作为 void* 存储在 m_Containers 中.这不是很好，但至少很简单.

IppDataType is enum, which values correspond to actual types. All management is done in template class TIppImageContainer<T>. And all specialization of this class is stored in m_Containers as a void*. It's not very good, but it is at least simple.

通过这种方法，我可以简单地实现模板 GetImage 方法，如下所示:

With this approach, I can simply implement template GetImage method like this:

template<class T> TIppImage<T>* CIppMemoryManager::GetImage(width, height)
{
  return reinterpret_cast<TIppImageContainer<T>*>(m_Containers[
    TIppTypeTraits<T>::ipp_data_type])->GetImage(width, height);
}

我使用特征类 TIppTypeTraits 从给定类型获取枚举值.

where I'm using traits class TIppTypeTraits<T> to obtain enum value from given type.

问题

我不能简单地实现像构造函数这样的非模板方法.我需要明确处理所有可能的类型:

I cannot simply implement non-template methods like constructor. I need to explicitly handle all possible types:

CIppMemoryManager::CIppMemoryManager()
{
  m_Containers[ipp8u] = new CIppImageContainer<Ipp8u>;
  m_Containers[ipp8s] = new CIppImageContainer<Ipp8s>;
  m_Containers[ipp16u] = new CIppImageContainer<Ipp16u>;
  m_Containers[ipp16s] = new CIppImageContainer<Ipp16s>;
  ...
}

更糟糕的是，对于析构函数，我还需要处理 void*:

Worse, for destructor I also need to deal with void*:

CIppMemoryManager::~CIppMemoryManager()
{
  delete reinterpret_cast<TIppImageContainer<Ipp8u>*>(m_Containers[ipp8u]);
  delete reinterpret_cast<TIppImageContainer<Ipp8s>*>(m_Containers[ipp8s]);
  delete reinterpret_cast<TIppImageContainer<Ipp16u>*>(m_Containers[ipp16u]);
  delete reinterpret_cast<TIppImageContainer<Ipp16s>*>(m_Containers[ipp16s]);
  ...
}

所以，问题是:

a) 有没有办法遍历不同类型的集合?此处不能使用traits 类，因为函数是非模板的.

a) Is there some way to iterate through collection of different types? Cannot use traits class here since function is non-template.

b) 有没有更好的方法来存储容器集合 - 不同类型的对象?当它们只是通用模板类的不同特化时，容器本身非常简单.

b) Is there some better way to store collection of containers - objects of different type? When they are just a different specialization of common template class, containers itself are pretty simple.

推荐答案

多态 CIppImageContainer(让它们共享一个公共基类)和智能指针有什么问题?

What's wrong with polymorphic CIppImageContainer<T> (make them all share a common base class) and a smart pointer ?

或者某种boost::variant?

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