向量迭代器类型未知

Question

I'm learning C++ and this is the first time I work with iterators

I have written down this code:

std::pair<max, max> ConvertToAStarMap::GetLimits(std::string map)
{
    // Init max and min variables.
    int max_x = std::numeric_limits<int>::min();
    int min_x = std::numeric_limits<int>::max();

    int max_y = max_x;
    int min_y = min_x;

    std::vector<std::string> map_cells = ConvertToAStarMap::split(map, ';');

    for (std::string::iterator it = map_cells.begin(); it != map_cells.end(); ++it)
}

And I get this error:

ConvertToAStarMap.cpp: In member function ‘std::pair<max, max> ConvertToAStarMap::GetLimits(std::__cxx11::string)’:
ConvertToAStarMap.cpp:31:52: error: conversion from ‘std::vector<std::__cxx11::basic_string<char> >::iterator {aka __gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >}’ to non-scalar type ‘std::__cxx11::basic_string<char>::iterator {aka __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >}’ requested
     for (std::string::iterator it = map_cells.begin(); it != map_cells.end(); ++it)
                                     ~~~~~~~~~~~~~~~^~
ConvertToAStarMap.cpp:31:59: error: no match for ‘operator!=’ (operand types are ‘std::__cxx11::basic_string<char>::iterator {aka __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >}’ and ‘std::vector<std::__cxx11::basic_string<char> >::iterator {aka __gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >}’)
     for (std::string::iterator it = map_cells.begin(); it != map_cells.end(); ++it)
                                                        ~~~^~~~~~~~~~~~~~~~~~

What is wrong? I don't understand it.

Answer 1

Easiest to do is:

for (const auto& cell : map_cells)

If you don't want to use the range based for loop :

for (auto it = map_cells.begin();......

The problem is that You want to iterate over the vector, not over the string, so it should be:

for (std::vector<std::string>::iterator it = map_cells.begin();......

This information is available in the error in point 2. :

1. error: conversion from
2. 'std::vector<std::__cxx11::basic_string<char> >::iterator
3. {aka __gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > > }'
4. to non-scalar type
5. ' std::__cxx11::basic_string<char>::iterator
6. {aka __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> > }'