Running OpenCV code- error: ‘DescriptorMatcher’ was not declared in this scope

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I have installed the OpenCV on my machine along with the opencv_bridge. I am trying to use this script in my ROS package:

https://github.com/spillai/recognitio...

The problem is that when I include it in my file (like this):

#include "opencv2/core/version.hpp"
#include "flair.hpp"

I am getting this error:

/home/osboxes/catkin_ws/src/cipek/src/flair.hpp:71:11: error: ‘DescriptorMatcher’ was not declared in this scope
   cv::Ptr<DescriptorMatcher> _matcher;

There are many more errors which follow this one, but I don't want to put it all here, because it is long, unless someone needs it. I haven't modified the file from the GitHub repository. How can I fix this issue?