"Cannot assign a value in null context" - problem with DateTime

[Michal_Szymanski]

In item file I have:

DateTime WtrLastDate "Data ostatniego podlewania [%1$ta %1$tR]" <calendar> (Wtr)

and in a rule:

sendCommand(WtrLastDate,now)

and during execution I’ve got:
201710-07 14:18:02.962 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Error during the execution of startup rule 'Watering_garden_startup': Cannot assign a value in null context.

What is wrong with rule?

MIchal

[Udo_Hartmann]

Type Conversions

Attention: This article is now also available on the openHAB 2 documentation page. If you want to add improvements or additions, please do so there. http://docs.openhab.org/configuration/rules-dsl.html#conversions Interacting with Items in rules A frequent operation in rules is to calculate other values from Item states or compare Item states against other values or perform other operations that are either responses to changes in item states or intended to change the item state. For a complete…

… Please, whenever possible use the method rather than the action:

WtrLastDate.sendCommand(now)

[jwiseman (Mr. Wiseman (OH 4.3.0 Snapshot on Pi4))]

@Udo_Hartmann

whenever possible use the method rather than the action

Hi Udo,

Looking for some advise on this topic:

Here are my variables in the rule file.

var Number		currMonth		= now.getMonthOfYear
var Number		currDay 		= now.getDayOfMonth
var Number		currDayofWeek	= now.getDayOfWeek 
var Number		currHour	    = now.getHourOfDay

I have numerous rules referencing these variables; which I do an update on them prior to checking them in the rule itself below:

rule "Kitchen HUE Motion Sensor 7 am - 5 pm"
    when
    	Item Kitchen_Motion_Sensor received update
    then

		currHour = now.getHourOfDay
		currMonth = now.getMonthOfYear

    	if (Kitchen_Motion_Sensor.state == ON && currHour >= 7  && currHour <= 17 && Home_Away.state == ON && KitchenSensor_Luminance.state <= 70 ) {			// hours 7 am to 5 pm
...

This all works but I get a TON errors during startup like this which I’m assuming is because of these 2 lines in the rule.

		currHour = now.getHourOfDay
		currMonth = now.getMonthOfYear

The errors during a clean boot up:

2018-12-10 09:37:52.723 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Kitchen HUE Motion Sensor 7 am - 5 pm': The name 'now' cannot be resolved to an item or type; line 995, column 14, length 3
2018-12-10 09:37:52.726 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Kitchen HUE Motion Sensor 10 pm - 12 am': The name 'now' cannot be resolved to an item or type; line 1151, column 14, length 3
2018-12-10 09:37:52.729 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Loft HUE Motion Sensor 7 am - 5 pm': The name 'now' cannot be resolved to an item or type; line 1073, column 14, length 3
2018-12-10 09:37:52.732 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Kitchen HUE Motion Sensor 7 am - 5 pm': The name 'now' cannot be resolved to an item or type; line 995, column 14, length 3
2018-12-10 09:37:52.734 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Kitchen HUE Motion Sensor 10 pm - 12 am': The name 'now' cannot be resolved to an item or type; line 1151, column 14, length 3
2018-12-10 09:37:52.736 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Loft HUE Motion Sensor 7 am - 5 pm': The name 'now' cannot be resolved to an item or type; line 1073, column 14, length 3

I’m running OH2.3 on a Synology NAS.

My gut feel tells me to make these items vs. variables?

What is your recommendation on fixing this?

Best, Jay

[Udo_Hartmann]

First of all: Why using a var at all?
Secondly, you have to define the var before using it.