如何在c ++迭代器类型中包装std :: chrono

Question

我尝试创建接收特定时间类型的模板参数的迭代式,说std::seconds,std::hours等等,我希望它获得作为参数2点的值表示time_points指定的持续时间,并能够使用这样的构建在基于循环的范围内,time_point通过以该持续时间或可能具有指定持续时间为单位增加电流,如下所示:

DateRange<std::seconds> dr(now() , 50);
for(auto d : dr){
 // do something at unit time
}

我试图用这种方式实现它

   using namespace std::chrono;
   template<typename Duration , typename Clock_t = high_resolution_clock, 
   typename Time_type = time_point<Clock_t, typename Duration> , typename 
   Time_pointer = Time_type* >
 class DateRange {
   using Time_type_t = typename Time_type::duration;
 public:
   DateRange(Time_type_t start, Time_type_t end) :
    m_begin(start),
    m_end(end)
   {

   }
   DateRange(Time_type_t end):
    m_begin(Clock_t::now())

   {

   }
   Time_pointer begin(){
    return &m_begin;
   }
   Time_pointer end() {
    return &m_end;
    }

    Time_pointer operator++(){
    present +=Duration(1);
    return present_point;
   }

 Time_type operator*(){
    return present;
  }

private:
Time_type m_begin;
Time_type m_end;
Time_type present;
Time_pointer present_point = &present;
Clock_t l_clock;
};
int main()
{
DateRange<seconds> dr(40s);
dr.operator++();
    std::cout << (*dr).time_since_epoch().count();
 }

'std :: chrono :: time_point :: time_point(std :: chrono :: time_point &&)':无法将参数1从'std :: chrono :: steady_clock :: time_point'转换为'const _Duration&'DateRange at 19

Answer 1

您返回的值begin最终需要等于您返回的值end一定量++。目前，这是否可能尚未指定，因为您返回指向不同对象的指针。

您可能需要一个单独的iterator类型。

template<typename Duration, typename Clock = high_resolution_clock>
class DateRange {
   using Time_type = time_point<Clock, Duration>;

   class iterator {
     iterator & operator++(){
       present += Duration(1);
       return *this;
     }

     iterator operator++(int){
       iterator res = *this;
       ++res;
       return res;
     }

     Time_type * operator->(){
       return &present;
     }

     Time_type operator*(){
       return present;
     }

     Time_type present;
   };

   Time_type m_begin;
   Time_type m_end;
public:
  DateRange(Time_type_t start, Time_type_t end) :
    m_begin(start),
    m_end(end)
    {}
  DateRange(Time_type_t end) :
    m_begin(Clock::now()),
    m_end(end)
    {}
  iterator begin(){
    return m_begin;
  }
  iterator end() {
    return m_end;
  }
};