EnumerableClass.h

#pragma once
 
 
template <typename Derived, typename Base = plNoBase>
class plEnumerable : public Base
{
public:
  plEnumerable()
  {
    if (Derived::s_pFirstInstance == nullptr)
      Derived::s_pFirstInstance = this;
    else
      Derived::s_pLastInstance->m_pNextInstance = this;
 
    Derived::s_pLastInstance = this;
    m_pNextInstance = nullptr;
    ++Derived::s_uiInstances;
  }
 
  virtual ~plEnumerable()
  {
    --Derived::s_uiInstances;
    plEnumerable* pPrev = nullptr;
    plEnumerable* pCur = Derived::s_pFirstInstance;
 
    while (pCur)
    {
      if (pCur == this)
      {
        if (pPrev == nullptr)
          Derived::s_pFirstInstance = m_pNextInstance;
        else
          pPrev->m_pNextInstance = m_pNextInstance;
 
        if (Derived::s_pLastInstance == this)
          Derived::s_pLastInstance = pPrev;
 
        break;
      }
 
      pPrev = pCur;
      pCur = pCur->m_pNextInstance;
    }
  }
 
protected:
  plEnumerable* m_pNextInstance;
};
 
#define PL_DECLARE_ENUMERABLE_CLASS(self) PL_DECLARE_ENUMERABLE_CLASS_WITH_BASE(self, plNoBase)
 
#define PL_DECLARE_ENUMERABLE_CLASS_WITH_BASE(self, base) \
private:                                                  \
  using plEnumerableBase = base;                          \
  friend class plEnumerable<self, base>;                  \
  static plEnumerable<self, base>* s_pFirstInstance;      \
  static plEnumerable<self, base>* s_pLastInstance;       \
  static plUInt32 s_uiInstances;                          \
                                                          \
public:                                                   \
  static self* GetFirstInstance()                         \
  {                                                       \
    return (self*)s_pFirstInstance;                       \
  }                                                       \
  self* GetNextInstance()                                 \
  {                                                       \
    return (self*)m_pNextInstance;                        \
  }                                                       \
  const self* GetNextInstance() const                     \
  {                                                       \
    return (const self*)m_pNextInstance;                  \
  }                                                       \
                                                          \
private:
 
#define PL_ENUMERABLE_CLASS_IMPLEMENTATION(self)                                \
  plEnumerable<self, self::plEnumerableBase>* self::s_pFirstInstance = nullptr; \
  plEnumerable<self, self::plEnumerableBase>* self::s_pLastInstance = nullptr;  \
  plUInt32 self::s_uiInstances = 0