c++ - 模板类和运算符重载

Question

如何重载如下所示的模板类？

template <class T>
const_iterator& List<T>::const_iterator::operator++()
{
  current = current->next;
  return *this;
}

template <class T>
const_iterator List<T>::const_iterator::operator++(int)
{
  const_iterator old = *this;
  ++( *this );
  return old;
}

我收到如下错误:

List.cpp:17: error: expected constructor, destructor, or type conversion before ‘&’ token
List.cpp:23: error: expected constructor, destructor, or type conversion before ‘List’
List.cpp:30: error: expected constructor, destructor, or type conversion before ‘&’ token
List.cpp:35: error: expected constructor, destructor, or type conversion before ‘List’

Answer 1

template <class T>
typename List<T>::const_iterator& List<T>::const_iterator::operator++()

在指定返回类型时，您不在所谓的 List<T> 的词法范围内.由于没有类型 const_iterator在封闭范围内，您会收到一个错误(恕我直言，尽管那个错误可能会表现得更好一点)。

C++11 的另一个选项可能是尾随返回类型:

template<class T>
auto List<T>::const_iterator::operator++()
    -> const_iterator&
{
  // ...
}

但是，最好的办法是在类本身中内联定义这些东西。您对课外定义有特殊原因吗？