相关疑难解决方法(0)

在模板,在那里,为什么我必须把typename和template上依赖的名字呢？究竟什么是依赖名称？我有以下代码:

template <typename T, typename Tail> // Tail will be a UnionNode too.
struct UnionNode : public Tail {
    // ...
    template<typename U> struct inUnion {
        // Q: where to add typename/template here?
        typedef Tail::inUnion<U> dummy; 
    };
    template< > struct inUnion<T> {
    };
};
template <typename T> // For the last node Tn.
struct UnionNode<T, void> {
    // ...
    template<typename U> struct inUnion {
        char fail[ -2 + (sizeof(U)%2) ]; // Cannot be instantiated for any …

当我在Visual Studio 2005中编译此代码时:

  template <class T>
  class CFooVector : public std::vector<CFoo<T>>
  {
  public:
    void SetToFirst( typename std::vector<CFoo<T>>::iterator & iter );
  };

  template <class T>
  void CFooVector<T>::SetToFirst( typename std::vector<CFoo<T>>::iterator & iter )
  {
    iter = begin();
  }

我收到这些错误:

c:\home\code\scantest\stltest1\stltest1.cpp(33) : error C2244:     'CFooVector<T>::SetToFirst' : unable to match function definition to an existing declaration
    c:\home\code\scantest\stltest1\stltest1.cpp(26) : see declaration of 'CFooVector<T>::SetToFirst'
    definition
    'void CFooVector<T>::SetToFirst(std::vector<CFoo<T>>::iterator &)'
    existing declarations
    'void CFooVector<T>::SetToFirst(std::_Vector_iterator<_Ty,_Alloc::rebind<_Ty>::other> &)'

如果我将一个typedef添加到CFooVector模板,我可以获得编译和工作的代码:

  template <class T>
  class CFooVector : public std::vector<CFoo<T>>
  {
  public:
    typedef typename …