rulesDSL maths

Setup, Configuration and Use Beginners
5

I am so glad I no longer need to do such type gymnastics. In jruby:

rule "solaredge.selfconsumption" do
  changed SolarEdge_Live_Consumption
  run do
    self_consumption = [SolarEdge_Live_Production - SolarEdge_Live_Consumption, 0].max | 'kW'   
    SolarEdge_Live_Self_Consumption.update(self_consumption) 

    logger.info("self consumption: #{self_consumption}")
  end
end

Basically you just use the item name. It is automatically inferred that they’re a numeric type and you can perform arithmetic as if they’re a number, but you can also treat them like a first class openhab items, with so many capabilities, such as:

  • SolarEdge_Live_Self_Consumption.meta['namespace'] to access its metadata,
  • SolarEdge_Live_Self_Consumption.persist to tell it to persist to the database,
  • SolarEdge_Live_Self_Consumption.average_since(24.hours, :influxdb) to get the persistence average data,
  • SolarEdge_Live_Self_Consumption.update '12kW' to update it with a string with UoM, and many more.

Note if your Production is less than Consumption, your code will give you a negative self consumption. I’m not sure that’s what you wanted? My code above will set the self consumption to zero in this case.

A bit of note if you’re not familiar with ruby:
self_consumption.zero? is just a preferred way of writing self_consumption == 0 or self_consumption == '0 W'. You can use any of the 3 variations.

[x, y, z] is an array, in this case [SolarEdge_Live_Production - SolarEdge_Live_Consumption, 0] is an array containing two elements: the calculation result and zero. Then you call [array].max to get the max of the elements. It’s the same as the traditional way of doing max(x, y) in other languages.