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:

SMACC/smacc/include/smacc/impl/smacc_state_machine_impl.h

Lines 208 to 224 in e5abc09

	void ISmaccStateMachine::setGlobalSMData(std::string name, T value)
	{
	{
	std::lock_guard<std::recursive_mutex> lock(m_mutex_);
	// ROS_WARN("set SM Data lock acquire");
	globalData_[name] = {[this, name]() {
	std::stringstream ss;
	auto val = any_cast<T>(globalData_[name].second);
	ss << val;
	return ss.str();
	},
	value};
	}
	this->updateStatusMessage();
	}

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.

┆Issue is synchronized with this Jira Task by Unito

[yassiezar]

The function object is used to serialise the stored data so that it could easily be printed to the terminal, as used here.

You should rather consider using a SMACC component to make complex data available between different states.