Add a vector<string> field to a cMessage - omnet++

Question

I'm building a custom cMessage that includes vectors as some fields. I have no issue with int or double vectors, but with string vectors, I get an error. Below is a sample message definition to reproduce the issue.
cplusplus {{
#include <vector>
typedef std::vector<int> IntVector;
typedef std::vector<string> StrVector;
}};
class IntVector { #existingClass; };
class StrVector { #existingClass; };
message sampleMessage extends cMessage
{
IntVector SampleIntVector;
StrVector SampleStrVector;
}
In my code, I have the below block
sampleMessage *msg = new sampleMessage();
vector<int> intVect = {1,2};
vector<string> stringVect;
string inputString = "dummy string";
stringVect.push_back(inputString);
msg->setSampleIntVector(intVect);
msg->setSampleStrVector(stringVect);
Using OMNeT++ version 6.0 pre10, at the 7th line, I get the error below suggesting the cMessage is expecting a vector<char *>
error: no viable conversion from 'vector<std::string>' to 'const vector<char *>'
I also tried on OMNeT++ version 5.6.2 and got a different error message. For clarity, the file testModel_m.cc is generated by OMNeT++.
testModel_m.cc:170:13: error: use of overloaded operator '<<' is ambiguous (with operand types 'std::ostream' (aka 'basic_ostream<char>') and 'const std::__cxx11::basic_string<char>')
out << *it;
~~~ ^ ~~~
testModel_m.cc:2040:45: note: in instantiation of function template specialization 'operator<<<std::__cxx11::basic_string<char>, std::allocator<std::__cxx11::basic_string<char> > >' requested here
case 1: {std::stringstream out; out << pp->getSampleStrVector(); return out.str();}
^
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/basic_string.h:6416:5: note: candidate function [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]
operator<<(basic_ostream<_CharT, _Traits>& __os,
^
testModel_m.cc:158:22: note: candidate function [with T = std::__cxx11::basic_string<char>]
inline std::ostream& operator<<(std::ostream& out,const T&) {return out;}
If I change the vector to char *, it works, but for my use case, I would need a vector of string since I search for values in a vector and with char *, that doesn't work quite well.
Is there a way to have a vector<string> field as part of the custom cMessage?

Answer 1

The workaround for the error use of overloaded operator '<<' is ambiguous is adding own definition of operator<< inside cplusplus {{ }} block, for example:
cplusplus {{
#include <vector>
typedef std::vector<int> IntVector;
typedef std::vector<std::string> StrVector;
std::ostream& operator<<(std::ostream &os, const StrVector& vec) {
std::stringstream out;
for (auto i : vec) {
out << i << ", ";
}
return os << out.str();
};
}};
class IntVector { #existingClass; };
class StrVector { #existingClass; };
message sampleMessage {
IntVector SampleIntVector;
StrVector SampleStrVector;
}