xtypes and $current

[bell...@gmail.com]

I’m using $current.obs where obs is an xtype.

The xtype is not in the current record, so a record is retrieved from the db. But then the current record is passed into the xtype system. But, the necessary values to calculate the xtype are not in the current record. So calculating the xtype fails.
So maybe if the xtype fails with the current record, it needs to try with the record from the db? That sounds a bit messy…

Here is a link to the line in question.
https://github.com/weewx/weewx/blob/548bf5eccc5bba35eeefe482fe4fd1b95f364f06/bin/weewx/tags.py#L599

A reasonable workaround for me is to $latest.
Thanks!
rich

[Tom Keffer]

It's up to the implementation of get_scalar() to decide whether to use the "current" record, or to retrieve a type from the database. Obviously, if it's not in the record, it should get the necessary ingredients for the xtypes calculation from either the record, or from the database.

What observation type are you trying to calculate? That is, what implementation of get_scalar() are you referring to?

-tk

--
You received this message because you are subscribed to the Google Groups "weewx-development" group.
To unsubscribe from this group and stop receiving emails from it, send an email to weewx-developm...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-development/3d6dfa2a-8cb9-40ae-8631-7981210bc041n%40googlegroups.com.

[bell...@gmail.com]

Tom,
I know I am on the fringe (or beyond it) of doing supported things, so I really appreciate your patience.
First, I am using $current with a data_binding because I have multiple databases. Noting that $current would do the lookup, this was just me being lazy (or it maybe at the time I felt it was more consistent for every observation to use $current). As I noted, I can easily use $latest for the xtype and its dependencies.
Second, I am not actually using $current. Because of the way cheetah processes ‘dynamic’ templates, I have moved much of the javascript generation into pure python. So, I am interacting with WeeWX ‘tag’ code directly from python.  Hence my note about not fully supported.
Thirdly, I am using John Kline’s AQI xtype (https://github.com/chaunceygardiner/weewx-airlink). I only wanted the xtype (I don’t have an airlink), so I wrote a service to just load the xtype. Again, I know I am off the support path.
After writing all this, I realize that I should just $latest(or its equivalent). I don’t think there is a good solution for WeeWX or the AQI xtype to handle this case. I am fine with the xtype expecting the dependency to be in the record. It doesn’t know it is being called in the ‘current context’, so a db lookup to get the latest seems ‘wrong’. I guess if a data_binding is passed into CurrentObj, WeeWX could pass the db record into the xtype system. But really the skin developer could just use $latest.
 I just wanted to note that there are some complexities/intricacies with xtypes and $current and hopefully save someone some time.
Lastly, thanks again to you, Matthew, Gary, and everyone that has contributed to WeeWX. It says a lot about its design and implementation that I can ‘abuse’ it. And thanks for the great support.
rich

[bell...@gmail.com]

Hmmm, if (big if) I am understanding the code correctly, I don’t think $latest will work for me. I think it is just calling CurrentObj with a data_binding.
Time to do some more learning.
- rich