setGlobalSMData not working with "non-streamable" objects

[dave992]

I was looking for a way to transfer data between states. In particular a std::filesystem::path and a Eigen::Isometry3d object.

For this purpose, I came across the setGlobalSMData and getGlobalSMData functions that the state machine support. As the functions are templated, it looked like they would support any type.

However, when I try to store an Eigen::Isometry3d object using setGlobalSMData, I get the following error:

error: no match for ‘operator<<’ (operand types are ‘std::stringstream’ {aka ‘std::__cxx11::basic_stringstream<char>’} and ‘Eigen::Transform<double, 3, 1>’)

The source code for setGlobalSMData:

https://github.com/robosoft-ai/SMACC/blob/e5abc09c51b16a8911b2516892afc953a00020ea/smacc/include/smacc/impl/smacc_state_machine_impl.h#L208-L224

The build error is due to the val object (casted to Eigen::Isometry3d) being inserted into the stream. As the object does not define a << operator, this results in the abovementioned error.

Why is globalData_ of type std::map<std::string, std::pair<std::function<std::string()>, boost::any>> and not just std::map<std::string, boost::any>>? The first element of the std::pair is not used in getGlobalSMData so I am not sure why we need the function object.

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