c++ - 如何避免 C++ 中 operator== 实现的错误？

Question

我经常有提供简单的逐个成员比较的类:

class ApplicationSettings
{
public:
   bool operator==(const ApplicationSettings& other) const;
   bool operator!=(const ApplicationSettings& other) const;

private:
   SkinType m_ApplicationSkin;
   UpdateCheckInterval m_IntervalForUpdateChecks;
   bool m_bDockSelectionWidget;
   // Add future members to operator==
};

bool ApplicationSettings::operator==(const ApplicationSettings& other) const
{
   if (m_ApplicationSkin != other.m_ApplicationSkin)
   {
      return false;
   }

   if (m_IntervalForUpdateChecks != other.m_IntervalForUpdateChecks)
   {
      return false;
   }

   if (m_bDockSelectionWidget != other.m_bDockSelectionWidget)
   {
      return false;
   }

   return true;
}

bool ApplicationSettings::operator!=(const ApplicationSettings& other) const;
{
   return ( ! operator==(other));
}

Given that C++ at this time does not provide any construct to generate an operator== , 除了我在数据成员下方添加的评论之外，是否有更好的方法来确保 future 的成员成为比较的一部分？

Answer 1

它并不能捕捉到所有情况，令人恼火的是它依赖于编译器和平台，但一种方法是 static_assert基于 sizeof类型:

static_assert<sizeof(*this) == <n>, "More members added?");

哪里<n>是 constexpr .

如果引入新成员，通常情况下，sizeof更改，您将导致编译时失败。