迭代c ++ map时<运算符丢失

Question

以下代码不想编译.请参阅包含的错误消息.

码:

#include <map>
#include <vector>
#include <iostream>

class MapHolder {
public:
    std::map<std::vector<std::string>,MapHolder> m_map;

    void walk_through_map() {
        std::map<std::vector<std::string>,MapHolder>::iterator it;
        for(it = m_map.begin(); it < m_map.end(); ++it) {
            it->second.print();
        }
    }

    void print() { std::cout << "hey" << std::endl; }
};

int
main(int argc, char *argv[])
{
    MapHolder m;
    m.walk_through_map();
}

错误:

$ g++ test.cc -O test
test.cc: In member function 'void MapHolder::walk_through_map()':
test.cc:12: error: no match for 'operator<' in 'it < ((MapHolder*)this)->MapHolder::m_map.std::map<_Key, _Tp, _Compare, _Alloc>::end [with _Key = std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, _Tp = MapHolder, _Compare = std::less<std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, _Alloc = std::allocator<std::pair<const std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, MapHolder> >]()'

之前我曾多次使用过这种类型的地图和迭代过程.这有什么问题？怎么解决呢

(代码看起来毫无意义,但这是一个减少的样本,仍然应该工作)

Answer 1

使用!=代替<in iterator比较.