问题
I'm using boost::program_options to parse the command line for my program and am having trouble trying to read a value into a public enum in a class which is also in a namespace.
Specifics:
Boost 1.44.0
g++ 4.4.7
I tried following the process spelled out in Boost Custom Validator for Enum but it isn't working for me.
Parameters.h
#include <istream>
namespace SA
{
class Parameters
{
public:
enum Algorithm
{
ALGORITHM_1,
ALGORITHM_2,
ALGORITHM_3,
ALGORITHM_4
};
friend istream& operator>> (istream &in, Parameters::Algorithm &algorithm);
Algorithm mAlgorithm;
<More Parameters>
}
}
Parmaeters.cpp
#include <boost/algorithm/string.hpp>
using namespace SA;
istream& operator>> (istream &in, Parameters::Algorithm &algorithm)
{
string token;
in >> token;
boost::to_upper (token);
if (token == "ALGORITHM_1")
{
algorithm = ALGORITHM_1;
}
else if (token == "ALGORITHM_2")
{
algorithm = ALGORITHM_2;
}
else if (token == "ALGORITHM_3")
{
algorithm = ALGORITHM_3;
}
else if (token == "ALGORITHM_4")
{
algorithm = ALGORITHM_4;
}
else
{
throw boost::program_options::validation_error ("Invalid Algorithm");
}
return in;
}
main.cpp
#include <boost/program_options.hpp>
using namespace SA;
int main (int argc, char **argv)
{
po::options_description options ("Test: [options] <data file>\n Where options are:");
options.add_options ()
("algorithm", po::value<Parameters::Algorithm>(&Parameters::mAlgorithm)->default_value (Parameters::ALGORITHM_3), "Algorithm");
<More options>
<...>
}
When I compile, I get the following error:
main.o: In function 'bool boost::detail::lexical_stream_limited_src<char, std::basic_streambuf<char, std::char_traits<char> >, std::char_traits<char> >::operator>><SA::Parameters::Algorithm>(SA::Parameters::Algorithm&)':
/usr/include/boost/lexical_cast.hpp:785: undefined reference to 'SA::operator>>(std::basic_istream<car, std:char_traits<char> >&, SA::Parameters::Algorithm&)'
I tried putting the operator>> in main and got the same error.
I've spent a couple of days on this now and am not where to go from here. If anyone has any ideas, it would be greatly appreciated.
回答1:
With your friend declaration, you declare
namespace SA {
istream& operator>> (istream &in, Parameters::Algorithm &algorithm);
}
And your implement in global namespace:
istream& operator>> (istream &in, Parameters::Algorithm &algorithm);
Move your implementation inside namespace SA
.
For you information:
namespace SA { void foo(); }
using namespace SA;
void foo() {} // implement ::foo and not SA::foo()
You have to use
namespace SA { void foo() {} }
or
void SA::foo() {}
来源:https://stackoverflow.com/questions/24310053/using-boostprogram-options-with-enum-in-class-in-namespace