To have Xcode generate C++ files with boilerplates and include guards that are compliant with the Coding Standard you can add an Xcode file template.
There's an excellent guide for that process here.
A zip file containing the High Fidelity file template can be found here.
As per the guide linked above, that folder should be placed in
~/Library/Developer/Xcode/Templates/File Templates/. You will need to create that if it does not exist.
With that folder in the right place, the next time you restart Xcode you should have a new category when you go to create a new file.
By selecting this type you will get a .cpp and a .h file with the name of your choosing that has boilerplates and include guards mostly pre-populated.
You will need to insert the sub-folder that contains your source file yourself, in the third line of the boilerplate.