Hi
I started to use RULE Areas to define component classes. KiCAD throws ERC error if Net Class is not defined also. The thing is I don’t want to define one net class for the rule area.
See the image. I’m actually fine with defining almost all of the nets as 50Ohm (it would even result in better and cleaner schematic), but not GND. How do I exclude GND?
I guess the rule area could be redrawn in a weird shape but I don’t like this solution.
Hmm, I think it’s a bug if you can’t just use a rule area to define component classes without also defining a net class. Can you give details on the error you see?
It looks like this
Net Class is undefined
Try deleting the Net Class field from the directive label properties
Yep, it does not throw the error anymore. A new directive label comes with both fields and with no indication that one should be deleted. Looks like a UI miss.
That was not my question anyway 
I’m perfectly OK with assigning Net classes but I have GND in the rule area that needs to be excluded somehow.
You can’t use a rule area to assign a netclass to only some of the nets in the rule area. So, you would either need to use a different rule area, individual directive labels, or change the shape of the rule area to exclude the GND net.
Well, one only needs to be deleted if you don’t want to assign a net class.
Yeah, that’s what I did, as seen on the original screenshot. It’s all an issue of clutter. Rule area seems like a much cleaner solution, but twisting its shape to avoid unneeded nets would look just as bad as multiple netclass directives, if not worse.
There is no indication that leaving the field empty is wrong. Seems very logical to not fill it rather than delete.
I wonder if we should report the ‘not defined’ error (and we should add ‘Component Class not defined’ too if that doesn’t exist) if and only if both fields are present and both are empty?
I, too, have noticed this and agree. This is not intuitive.