c++ - Boost字符串算法错误

Question

我对 boost 字符串算法库有疑问。我尝试使用 split 和 tokenize 来拆分/标记 wstring，但我总是遇到以下错误

代码

std::vector<std::wstring> tokenize(const std::wstring& input) {
    std::vector<std::wstring> output;
    boost::char_separator<wchar_t> sep(L";");
    boost::tokenizer<boost::char_separator<wchar_t>> tokens(input, sep);
    std::for_each(tokens.begin(), tokens.end(),
        [&output] (std::wstring ws) {
            output.push_back(ws);
        }
    );
    return output;
}

错误信息

 error C2664: 'std::_String_const_iterator<std::_String_val<std::_Simple_types<char>>>::_String_const_iterator
(const std::_String_const_iterator<std::_String_val<std::_Simple_types<char>>> &)' : 
cannot convert argument 1 
from 'std::_String_const_iterator<std::_String_val<std::_Simple_types<wchar_t>>>' 
to 'const std::_String_const_iterator<std::_String_val<std::_Simple_types<char>>> &'

我尝试过其他方法，例如 boost::split 或将 wstring 更改为 string，但它不起作用。

这里有什么问题吗？

Answer 1

查看tokenizer.hpp的源码，tokenizer是这样定义的:

  template <
    typename TokenizerFunc = char_delimiters_separator<char>, 
    typename Iterator = std::string::const_iterator,
    typename Type = std::string
  >
  class tokenizer {
  ...

您只为类模板指定了 TokenizerFunc，但忘记指定 Iterator 和 Type。结果，您收到了错误:cannot convert argument 1 ...wchar_t... to ...char...

为了让你的代码运行起来，你应该指定 boost::tokenizer 的所有参数，例如:

typedef boost::tokenizer<boost::char_separator<wchar_t>, std::wstring::const_iterator, std::wstring > tokenizer;

代码:

#include <stdlib.h>
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <boost/tokenizer.hpp>

std::vector<std::wstring> tokenize(const std::wstring& input) {
  std::vector<std::wstring> output;

  typedef boost::tokenizer<boost::char_separator<wchar_t>, std::wstring::const_iterator, std::wstring > tokenizer;
  boost::char_separator<wchar_t> sep(L";");
  tokenizer tokens(input, sep);

  std::for_each(tokens.begin(), tokens.end(),
    [&output] (std::wstring ws) {
      output.push_back(ws);
    }
  );

  return output;
}

int main(int argc, char* argv[]) {

  auto v = tokenize(L"one;two;three");
  std::copy(v.begin(), v.end(), std::ostream_iterator<std::wstring, wchar_t>(std::wcout, L" "));

  return EXIT_SUCCESS;
}

输出:

one two three