UoM calculations

[rossko57]

@powerpolly

I’d like to calculate with temperature items. so I thought I must convert the UoM to a simple Number

Better to calculate with the quantities with units.

Working with Number:Temperature Items in rules

openHAB provides Quantity Type features, which can seem baffling. On top of that, Temperature type Quantities have a few quirks all of their own. These notes intend to guide the rules author. I’ve shown work examples in DSL rules language, see below for other scripts examples. All have similar features, if different syntax. Knowing what can be done is half the battle. What is a Quantity Type? Simply, Item states and rule variables may contain Quantities - that just means a number AND a unit …

Also shows you how to get “just the number” in the unit of your choice, if you rally must go that way.

var Number tempC= (Buderus_Aussentemperatur.state as QuantityType<Temperature>).toUnit("°C")  
// that gets temp in C regardless of original unit
var Number hyst = temp + 0.3 | °C
// that adds a quantity in C, result is a quantity in C
logInfo("loggerName", "message: "+  hyst + "  " + temp)

EDIT - my mistake, do not use var Number here, just var will do