I'm new to Magento and I'm creating a module that adds two attributes to products via a Setup/InstallData class and using EavSetupFactory. This is working fine and I've got a class passed via the 'backend' key in the array passed to addAttribute() to handle validation. That's also working OK, I can check the submitted value of the attribute and throw an exception if it fails validation. The problem is I can't see how I can compare it to the other custom attribute, I can only write code that validates one attribute at a time. I've looked at attribute sets and groups but they don't seem to be the right thing. Can anyone point me in the right direction?
