Hi all,
A beginners question I guess:
I want to create some custom objects (for the moment just representing rectangles, but in the future they will represent objects in physics events) and add these to a root tree. Once in the root tree I want to use a macro to plot histograms of the different rectangles area (calling the Rectangle::area() method, again this will eventually be more complex).
Am I right in thinking I need to have Rectangle inherit from TObject and then TObject::Write() the object into a tree? And then for the macro add the Rectangle to root/cint? Are there any examples of how to do this? I’ve spent the last 3 days looking for some example code but have yet to find any, perhaps I’m looking in the wrong places 
Thanks for any and all help
Simon
Hi Simon,
look at http://root.cern.ch/root/CintGenerator.html. Note that there is no reason to have a standalone program, or a Makefile. You can simply create the library (including the dictionary) and load it by running “.L Track.C+” in the above example. But the example shows you what the code should look like.
Axel.
Ok I now have working code adding in objects. (Woo hooo!) I’d like to have these objects in branches of my TTree a la root.cern.ch/root/HowtoWriteTree.html so I’ve copied the code from the example changing the relevant lines, eg:
However when I run the code I get:
Now my program knows about CMyRectangle objects (it makes them and saves them into the Tree), but the Branch method doesn’t know about them. How do I get the Branch method to find my CMyRectangle class?
Cheers
Simon
Ahh posted before I saw your reply 
I guess I need to do something similar to solve this problem Axel?
Cheers
Simon
Hi Simon,
yepp, create a dictionary. That will be done automatically if you create your lib with “.L MyRectangle.C+” (or .cxx+,…) and if the header file declaring CMyRectangle has the same name as the source file you’re loading, only with a .h / .hxx / .hpp extension (e.g. MyRectangle.h) . Otherwise you’ll need a linkdef.h; see http://root.cern.ch/root/RootCintMan.html on that.
Axel.
Hello. The link you provided is now defunct - would you be able to provide an updated one? With many thanks!