Item name as variable?

[rockit4 (D)]

Hi all,

I tried to search the forum about storing item names as variables in rules, some seems to get it working and others do not. Is this possible?

For example how can I make this work without getting "An error occurred during the script execution: Could not invoke method: org.eclipse.smarthome.model.script.actions.BusEvent.sendCommand(java.lang.String,java.lang.String) on instance: null
"?

rule "Please make it work"
when
        Member of gTest changed
then
          var triggerItem = triggeringItem.name
          var itemName = triggerItem.substring(0, triggerItem.length - 4).toString
          sendCommand(itemName, ON) //edit :)
end

My dilemma is that I have two sets of variables: “theGoodStuff” and “theGoodStuff_tmp”.
And something is happening in “theGoodStuff_tmp” and I want to process that and store it in the “theGoodStuff”. So I strip the “_tmp” part and hope to send it

[rossko57]

@rockit4

sendCommand(itemName, On)

On is not a string
Try “On” , or better “ON” for a Switch type Item.

[rockit4 (D)]

Funny that you should say that. You helped someone with the exact same problem where the error was that he tried to get SUM from a switch. But please ignore the faults caused by me trying to simplify

[SOLVED] Use variable (item.name) with sumSince

Hey, I´m trying to get the sum of my persisted item-states (influxdb) with a rule. Everything works fine when I use the item-name itself, but if I try to make this rule more generic, sumSince can´t handle the item.name stored in a variable: *.items (for each room) Switch WhnZ_BewegungSensor_Switch "Bewegung [MAP(motion.map):%s]" (gPresence) { channel="hue:0107:huebridge:presence_whnz:presence" } Number WhnZ_BewegungSensor_Occupancy "Wohnzimmer [%s]" …

[rlkoshak (Rich Koshak)]

For more discussion on this sort of approach, see Design Pattern: Associated Items. Though I’m not sure that I emphasize the fact that both arguments to the sendCommand and postUpdate Actions must be Strings which is what tripped you up here.

[rossko57]

It’s not really clear what you state you are at now,

@rockit4

sendCommand(itemName, ON) //edit

ON is not a string either. Try “ON”

[rockit4 (D)]

In this example we could imagine that I try to send to a switch item. The focus should be at using the variable as item name.

[rossko57]

You should stop showing us examples with errors in if you don’t want them corrected.

I begin to think you are not showing us ypur real rule for some reason. I’m not playing guessing games - sendCommand() is not complicated, just give it two strings.
If you get an error, you need to look at the supposed strings you are supplying.

[rockit4 (D)]

Did some more searching and reading and found the solution

[noppes123 (Ron)]

@rockit4

found the solution

Please share, so others can learn from it. ;o)

[rockit4 (D)]

Dont know if I dare

[noppes123 (Ron)]

We all make mistakes (and often the same “stupid” ones)…

[rockit4 (D)]

True

This worked for me:
I created a second group called gTest2 for the “theGoodStuff” items (the target for the processed value).
Then I used the following lines to:

1. Get the item that triggered the rule (theGoodStuff_tmp) and remove the “_tmp” part
2. Get the target item from the string “itemNameStr”
3. Send it to the theGoodStuff item.

val itemNameStr = triggeringItem.name.substring(0, triggeringItem.name.length - 4).toString // get trigger item and remove "_tmp"
var itemName = gTest2.members.findFirst[ t | t.name == itemNameStr ] as GenericItem //get target item
sendCommand(itemName, ON)

[5iver (Scott Rushworth)]

You might want to check this out too (someone should get this into the docs)…

[Rules DSL] Get item from string name!

For a couple years now, I’ve been wanting/looking for a way to construct an item from its name as a string. There are other ways to do this, and the most popular requires the item to be in a group, which can have it’s challenges. I’ll keep this short and SWEET… I finally figured it out, and it is extremely simple! For OH 2.x, you’ll need this import… import org.eclipse.smarthome.model.script.ScriptServiceUtil For OH 3.x, this import instead… import org.openhab.core.model.script.ScriptService…

[rossko57]

To revisit the original rule …

items

Group gTest
Switch theGoodStuff "switch me"
Switch theGoodStuff_tmp "switch me" (gTest)

rule (exact copy of original post)

rule "Please make it work"
when
        Member of gTest changed
then
          var triggerItem = triggeringItem.name
          var itemName = triggerItem.substring(0, triggerItem.length - 4).toString
          sendCommand(itemName, ON) //edit :)
end

openhab.log error message (exactly as reported)

2020-02-26 22:45:55.405 [ERROR] [ntime.internal.engine.RuleEngineImpl] - rule 'Please make it work': An error occurred during the script execution: Could not invoke method: org.eclipse.smarthome.model.script.actions.BusEvent.sendCommand(java.lang.String,java.lang.String) on instance: null

revised rule (quotemarks only added)

rule "Please make it work"
when
        Member of gTest changed
then
          var triggerItem = triggeringItem.name
          var itemName = triggerItem.substring(0, triggerItem.length - 4).toString
          sendCommand(itemName, "ON") //edit :)
end

demonstration of it working in events.log

2020-02-26 22:56:12.569 [ome.event.ItemCommandEvent] - Item 'theGoodStuff_tmp' received command OFF
2020-02-26 22:56:12.580 [vent.ItemStateChangedEvent] - theGoodStuff_tmp changed from ON to OFF
2020-02-26 22:56:12.585 [ome.event.ItemCommandEvent] - Item 'theGoodStuff' received command ON
2020-02-26 22:56:12.598 [vent.ItemStateChangedEvent] - theGoodStuff changed from NULL to ON

Seriously, all it needed was “ON” instead of ON

[bananajoe86]

Hey all, I have a simular question. With this example I got it, to definine a variable Item name. My next goal ist to figure out the state of this variable Item.

when 
   Item solarttttt received command  
then
    var Number  stunde = now.getHour() -10
    var triggerItem = "forecast" + stunde
    var itemName = triggerItem.toString
    var erste = itemName.state.toString
    logInfo("Solartest", "" + erste)  

Script execution of rule with UID ‘Solar-7’ failed: ‘state’ is not a member of ‘java.lang.String’; line 347, column 17, length 14 in Solar

Thx for help, Joe