Subtracting 2 hours from datetime item

Setup, Configuration and Use Scripts & Rules
1

Hello,

I have a DateTime item coming in from the ical binding showing me when something is going to happen from my calendar. I’m trying to take that item, subtract 2 hours from that and set that as a new dateitem’s value.

I’m trying to it is like this:


Calendar_Next_Event_Start_2Hour_Warning.postUpdate(Calendar_Next_Event_Start.minusHours(2))

This gives the following error:

2024-06-05 18:09:39.235 [ERROR] [internal.handler.ScriptActionHandler] - Script execution of rule with UID '8507d63e20' failed: Calendar_Next_Event_Start_2Hour_Warning.postUpdate(Calendar_Next_Event_Start. ___ minusHours(2))
   The method minusHours(int) is undefined for the type DateTimeItem; line 1, column 109, length 10

Any thoughts on how this can be done? I plan to use this new datetime item as a trigger on a rule.

2

Rules DSL

Calendar_Next_Event_Start_2Hour_Warning.postUpdate((Calendar_Next_Event_Start.state as DateTimeType).zonedDateTime.minusHours(2).toString())

In jruby

Calendar_Next_Event_Start_2Hour_Warning.update(Calendar_Next_Event_Start.state - 2.hours)
1 Like
3

@jimtng - Thanks for the quick reply! This works perfectly.

I had made some progress on this but was still missing the final .toString() bit. Appreciate the help!

4

For completeness here’s Blockly:

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image1694×142 22.6 KB

and JS Scripting

items.Calendar_Next_Event_Start_2Hour_Warning.update(time.toZDT(items.Calendar_Next_Event_start).minusHours(2));
1 Like
5

As a followup, if I want to take my newly created 2 hour warning item and use it as a time based trigger for another rule, will this work since it is a string type item?

6

If it’s a String Item then no, that won’t work. But why is it a String Item? It should be a DateTime Item. The String version of the DateTime passed as an update to the Item will get parsed into a DateTime, if it’s being sent to a DateTime Item and is parsable.

the need to call toString is really just a quirk of Rules DSL and is a way to work around it’s flakey typing system. You’ll notice that the call to toString isn’t there for any of the other languages.

7

Thanks @rlkoshak,

I think I made an error when I first created my new item and created it as a string item. I changed it to a datetime item and reran my rule and all is now set. Appreciate the explanation!

8

@rlkoshak would it be useful if we added an offset option to the DateTimeTrigger?

9

Yes! There is already an issue open to add that. Allow offset for "at the time specified in an item's state" trigger · Issue #4195 · openhab/openhab-core · GitHub

As far as I know no one has taken it upon themselves to add it but there is definitely interest and I think it would be an excellent feature.

1 Like
10

I have no idea how big of a use case this would fill, but I have two rules I want to use it for.

Thanks @jimtng!

11

https://github.com/openhab/openhab-core/pull/4271

1 Like
12

FYI This appears to be broken in 5.0.1 using rules DSL