C++:Boost program_options:多个参数列表

Question

我正在和我一起工作boost::program_options.我的程序应该作为任意长度的任意数量的"列表"作为参数(除其他外...).例如,用户应该能够打电话

./myprogram -list item1 item2 item3 -list item1 item2 -list item1 item2

显然,我不希望一个接一个地获得一个列表/向量与所有项目,但是(在这种情况下)三个列表/向量(或者,例如,包含元素的向量的一个向量)每个列表有两个或三个项目(每个项目应该是一个字符串,但我想这没关系).正如我之前所说,列表的数量(以及每个列表的项目数量!)应该是任意的.我怎么能这样做boost::program_options？

Answer 1

这可以在没有大量额外代码的情况下完成.秘诀是将解析步骤与存储步骤分开,如本答案中所做的那样.

解析器将返回一个键/值结构的容器,因为选项是从用户呈现的.如果多次提交选项,则容器将为每个选项提交单独输入.扫描特定选项并按我们想要的方式组织其值非常简单.

这是一个在单独的行上打印出每个输入多令牌选项的示例:

#include <iostream>
#include <string>
#include <vector>

#include <boost/program_options.hpp>

namespace po = boost::program_options;

int main(int argc, char *argv[]) {
   // Define a multi-token option.
   po::options_description desc("Allowed options");
   desc.add_options()
      ("list", po::value<std::vector<std::string>>()->multitoken(), "multiple values");

   // Just parse the options without storing them in a map.
   po::parsed_options parsed_options = po::command_line_parser(argc, argv)
      .options(desc)
      .run();

   // Build list of multi-valued option instances. We iterate through
   // each command-line option, whether it is repeated or not. We
   // accumulate the values for our multi-valued option in a
   // container.
   std::vector<std::vector<std::string>> lists;
   for (const po::option& o : parsed_options.options) {
      if (o.string_key == "list")
         lists.push_back(o.value);
   }

   // If we had other normal options, we would store them in a map
   // here. In this demo program it isn't really necessary because
   // we are only interested in our special multi-valued option.
   po::variables_map vm;
   po::store(parsed_options, vm);

   // Print out the multi-valued option, each separate instance on its
   // own line.
   for (size_t i = 0; i < lists.size(); ++i) {
      for (size_t j = 0; j < lists[i].size(); ++j)
         std::cout << lists[i][j] << ' ';
      std::cout << '\n';
   }

   return 0;
}

这是一个示例调用(在coliru现场):

$ ./po --list 1 2 3 --list foo bar --list how now brown cow
1 2 3 
foo bar 
how now brown cow