If You Suddenly Can’t Map Fields In a TemplaVoila Template…
Thought I'd write this up in case anyone else out there runs into the same thing.
If you use TemplaVoila as your template engine, you know that a big part of changing the look and feel of your site is changing the mapping of data structures to fields in the template.
But what if one day you're making changes to a template — say, adding a new field — and the field just won't save in the template? Even if you clear out the caches?
If this has happened to you, check your Apache error log. If you see a bunch of errors in there that look like this:
PHP Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource…
… then you can solve the problem by going into the Extension Manager and uninstalling, then reinstalling the TemplaVoila extension. Doing this fixes something in the database that is causing your problem. Once TemplaVoila is reinstalled, you will be able to map fields again.
Don't ask me why this works, I have no idea. But it does work.