[SOLVED] Scale-Transformation in Rule: Error "Could not invoke method: Transformation.transform() on instance: null

Setup, Configuration and Use Beginners
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1
  • Platform information:
    • Hardware: Raspberry Pi 4
    • OS: Raspbian 10 (OpenHABian)
    • Java Runtime Environment: OpenJDK 1.8.0_222
    • openHAB version: 2.4.0

Hello,

I am trying an Example of Marianne Spiller’s german OpenHAB 2 book (Chapter 6.3.5). A Status Summary item is created for wind speed and direction fetched from Yahoo Weather API. I was trying to do something similar with OpenWeatherAPI.
Transformation:
windDegreeToText.scale

[0..22.5]=Nord
]22.5..67.5]=Nordost
...
[..]=undefiniert

An Item, which works:

Text item=CurrentWindDirection label="Windrichtung [SCALE(windDegreeToText.scale):%s]" icon="wind"

The Summary Item

String SummaryStateWind //wetter.rules

and the rule wetter.rules:

rule "Status Summary Wind"
when
    Item CurrentWindSpeed changed or
    Item CurrentWindDirection changed
then
    var Number wg = ((CurrentWindSpeed.state as QuantityType<Number>).floatValue)
    logWarn("wetter.rules","CurrentWindDirection "+CurrentWindDirection)
    logWarn("wetter.rules","CurrentWindDirection.state "+CurrentWindDirection.state)
    logWarn("wetter.rules","(CurrentWindDirection.state as QuantityType<Number>) "+(CurrentWindDirection.state as QuantityType<Number>))
    logWarn("wetter.rules","(CurrentWindDirection.state as QuantityType<Number>).floatValue "+(CurrentWindDirection.state as QuantityType<Number>).floatValue)

    //var wr = transform("SCALE", "windDegreeToText.scale", (CurrentWindDirection.state as QuantityType<Number>).floatValue)
    var wr = transform("SCALE", "windDegreeToText.scale", 240.0f)
    var String Ausgabe = String::format("%1$.0f km/h aus " + wr, wg)
    SummaryStateWind.postUpdate(Ausgabe)
end

The result of this is

2019-10-10 23:49:10.015 [WARN ] [.smarthome.model.script.wetter.rules] - CurrentWindDirection CurrentWindDirection (Type=NumberItem, State=240.0 ?, Label=Wind direction, Category=wind, Groups=[gWetter])
2019-10-10 23:49:10.022 [WARN ] [.smarthome.model.script.wetter.rules] - CurrentWindDirection.state 240.0 ?
2019-10-10 23:49:10.027 [WARN ] [.smarthome.model.script.wetter.rules] - (CurrentWindDirection.state as QuantityType<Number>) 240.0 ?
2019-10-10 23:49:10.033 [WARN ] [.smarthome.model.script.wetter.rules] - (CurrentWindDirection.state as QuantityType<Number>).floatValue 240.0
2019-10-10 23:49:10.037 [ERROR] [ntime.internal.engine.ExecuteRuleJob] - Error during the execution of rule 'Status Summary Wind': An error occurred during the script execution: Could not invoke method: org.eclipse.smarthome.core.transform.actions.Transformation.transform(java.lang.String,java.lang.String,java.lang.String) on instance: null

The error occurs no matter which of the “var wr” lines is active. Even the MAP transformation raises the same error. The book example uses a MAP transformation as the Yahoo API delivered different values.
Any idea what I am doing wrong?

Thanks
Marcel

2

Not sure what that is supposed to represent. Try
var wr = transform("SCALE", "windDegreeToText.scale", "240.0")

1 Like
3

Thank you and sorry for the late reply, I was unexpectedly offline for a time.
The “f” was supposed to represent a float. Anyway, changing it to 240.0 raises exactly the same error. To me, it looks like the transform doesn’t work at all.

4

Did you use the quote marks? As it says in the error message, the transform() action expects three string parameters.

1 Like
5

Wow, I didn’t notice the quotes. Yes, that works, so the working line reads:

var wr = transform("SCALE", "windDegreeToText.scale", (CurrentWindDirection.state as QuantityType<Number>).floatValue.toString)

So “on instance null” just means it is a static method, not that something is wrong with the instance?

Thanks a lot, rossko!

1 Like
6

I’ve no idea of the technical term - practical experience says the rule engine usually means either a non-existent object or some kind of object that cannot be cast to the desired type.