使用我的自定义迭代器和stl算法

Question

我正在尝试创建自己的迭代器,并且我已经使用std :: generate算法按预期工作了.但是,当我尝试std :: find的std :: max_element时,我得到一些神秘的错误.

这是我的迭代器的接口:

template <typename GridT, 
          typename GridPtr,
          typename GridRef,
          template <typename> class ShapeT>
class GridIterator
{
public:
    typedef GridIterator<GridT, GridPtr, GridRef, ShapeT> Iterator;

    // Iterator traits - typedefs and types required to be STL compliant
    typedef std::ptrdiff_t           difference_type;
    typedef typename GridT::Element  value_type;
    typedef typename GridT::Element* pointer;
    typedef typename GridT::Element& reference;
    typedef size_t                   size_type;
    std::forward_iterator_tag        iterator_category;


    GridIterator(GridT& grid,
                 ShapeT<typename GridT::Resolution> shape,
                 Index iterStartIndex);

    ~GridIterator();

    Iterator& operator++();
    Iterator  operator++(int);

    typename GridT::Element& operator*();
    typename GridT::Element* operator->();

    bool operator!=(const GridIterator& rhs) const;
    bool operator==(const GridIterator& rhs) const; 
    ....

}

使用std :: find,我收到此错误

在/usr/include/c++/4.6/algorithm:63:0中的文件中,来自./grid/Map_Grid.h:11,来自main.cpp:4:/usr/include/c++/4.6/bits/stl_algo. h:在函数'_IIter std :: find(_IIter,_IIter,const _Tp&)[with _IIter = Map :: GridIterator,Map :: Grid*,Map :: Grid&,Map :: Rectangle>,_Tp = int]': main.cpp:103:50:从这里实例化/usr/include/c++/4.6/bits/stl_algo.h:4404:45:错误:没有匹配函数来调用'__iterator_category(Map :: GridIterator,Map :: Grid)*,Map :: Grid&,Map :: Rectangle>&)'/ usr /include/c++/4.6/bits/stl_algo.h:4404:45:注意:候选者是:/usr/include/c++/4.6/bits/ stl_iterator_base_types.h:202:5:注意:模板typename std :: iterator_traits :: iterator_category std :: __ iterator_category(const _Iter&)

使用std :: max_element:

在/usr/include/c++/4.6/bits/char_traits.h:41:0中的文件中,来自/usr/include/c++/4.6/ios:41,来自/usr/include/c++/4.6/ostream:40 ,来自/usr/include/c++/4.6/iostream:40,来自./grid/Map_GridIterator.h:7,来自./grid/Map_Grid.h:8,来自main.cpp:4:/ usr/include/c ++ /4.6/bits/stl_algobase.h:在函数'const _Tp&std :: max(const _Tp&,const _Tp&)[with _Tp = Map :: GridIterator,Map :: Grid*,Map :: Grid&,Map :: Rectangle> ]':main.cpp:102:60:
从这里实例化/usr/include/c++/4.6/bits/stl_algobase.h:215:7:错误:'__ <_ b'/ usr中的'operator <'不匹配/include/c++/4.6/bits/stl_algobase.h:215:7:注意:候选人是:/usr/include/c++/4.6/bits/stl_pair.h:207:5:注意:模板constexpr bool std :: operator <(const std :: pair <_T1,_T2>&,const std :: pair <_T1,_T2>&)/usr/include/c++/4.6/bits/stl_iterator.h:291:5:注意:模板bool std :: operator <(const std :: reverse_iterator <_Iterator>&,const std :: reverse_iterator <_Iterator>&)/usr/include/c++/4.6/bits/stl_iterator.h:341:5:note:te mplate bool std :: operator <(const std :: reverse_iterator <_IteratorL>&,const std :: reverse_iterator <_IteratorR>&)/usr/include/c++/4.6/bits/stl_iterator.h:1049:5:注意:模板bool std :: operator <(const std :: move_iterator <_IteratorL>&,const std :: move_iterator <_IteratorR>&)/usr/include/c++/4.6/bits/stl_iterator.h:1055:5:注意:模板bool std :: operator <(const std :: move_iterator <_Iterator>&,const std :: move_iterator <_Iterator>&)/usr/include/c++/4.6/bits/basic_string.h:2510:5:note:template bool std :: operator <(const std :: basic_string <_CharT,_Traits,_Alloc>&,const std :: basic_string <_CharT,_Traits,_Alloc>&)/usr/include/c++/4.6/bits/basic_string.h:2522: 5:注意:模板bool std :: operator <(const std :: basic_string <_CharT,_Traits,_Alloc>&,const _CharT*)/usr/include/c++/4.6/bits/basic_string.h:2534:5:note :template bool std :: operator <(const _CharT*,const std :: basic_string <_CharT,_Traits,_Alloc>&)/usr/include/c++/4.6/bits/stl_vector.h:1290:5:注意:模板bool的std ::操作符< (const std :: vector <_Tp,_Alloc>&,const std :: vector <_Tp,_Alloc>&)/usr/include/c++/4.6/tuple:586:5:注意:模板bool std :: operator <( const std :: tuple <_TElements ...>&,const std :: tuple <_Elements ...>&)

Answer 1

您缺少一个typedef关键字,用于声明指示迭代器类别的别名:

// Iterator traits - typedefs and types required to be STL compliant
//...
typedef std::forward_iterator_tag iterator_category;
~~~~~~^

没有typedef,你实际上是在声明一个数据成员.

为避免此类错误,您可以将std::iterator类模板用作基类,而不是自己定义这些别名:

class GridIterator : public std::iterator<std::forward_iterator_tag
                                        , typename GridT::Element>