Eigen::Ref<> as a member variable

Question

I need a class to have an Eigen::Ref variable as a static member which would be initialized through an init static method. Something like this:

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Answer 1

In your case you should very likely better use a VectorXd, otherwise you would have to make sure that the VectorXd you passed to init is never destroyed.

The only reason to use a Ref here would be to allow initializing data with, e.g., a column of a Matrix without any copy.

Finally, if you want to reassign a Ref to reference another buffer, then use a placement new to re-call the constructor of Ref. Don't forget to call the destructor first.