Make use of Group based rules

[NCO (E. Gerland)]

Raspberry with OH 2.5 M3 (openhabian).

I use @rlkoshak DP a lot - especially this one:

Design Pattern: Working with Groups in Rules

Please see Design Pattern: What is a Design Pattern and How Do I Use Them for how to read and use DPs. Problem Statement Often one finds a number of Rules that are very similar and that all work on similar Items resulting in a lot of duplicated code. One way to solve this problem is through the use of Groups. Concept [image] This DP is not a standard DP in that it provides a single concrete template to follow to solve a specific problem. Instead this DP is more of a grand exploration of some …

However, I wonder if my rule below - which is obviously wrong - could be realized somehow:

rule "Monitor Average Traveltime"
when
Member of G_Trvl changed
then
// get itemname and update avr time of this item
var itemName = triggeringItem.name.toString
var String itemNameStr = itemName + "_Avr"
var Number avr = itemName.averageSince(now.withTimeAtStartOfDay)
logInfo("office.rules", "Average Traveltime calculation")
itemNameStr.postUpdate(avr)
logInfo("office.rules", "Average Traveltime of " + itemName + ": ...")
end 

I guess this could be the key, but I don’t get it:

Reusable Functions: A simple lambda example with copious notes

Major Edit: Rewrote with the cleaner OH 2.3 syntax. The example lambda on the OH 1 wiki is overly complex and as written will not work in OH 2. This quick example will show a super simple lambda example with copious notes. Here is the code without comments. It takes in an Item, logs it’s state and returns a slightly modified version of the String logged. val log= [ GenericItem s | logInfo("lambda", s.state.toString) s.state.toString + " logged" ] rule "Call Lambda" when // some t…

[rossko57]

@NCO

var itemName = triggeringItem.name.toString
…
var Number avr = itemName.averageSince(now.withTimeAtStartOfDay)

itemName is just a string. You can’t get the .averageSince() of a string.
What you need is the proper Item object by that name.
There are ways to get hold of an Item if you only have its name as a string … but in this case you derived the name string directly from the Item object to begin with. You already have it, so -

var Number avr = triggeringItem.averageSince(now.withTimeAtStartOfDay)

@NCO

itemNameStr.postUpdate(avr)

Again, itemNameStr is just a string and you cannot .postUpdate() to a string, you need the Item object.
As said, there are ways to get hold of Item by name.

But fortunately the postUpdate action (as opposed to the dot-method) happens to able to do that for us - it wants two strings as parameters.
So in this rule, we can “cheat” and let postUpdate action find the Item for us.

postUpdate(itemNameStr, avr.toStrng)

[Olti]

Glad that I checked the thread again before sending my message. Otherwise there would be two same answers now.

An alternative to

@rossko57

postUpdate(itemNameStr, avr.toStrng)

would be to include

 import org.eclipse.smarthome.model.script.ScriptServiceUtil

and get the real item using

itemNameStr = ScriptServiceUtil.getItemRegistry.getItem(itemName + "_Avr")
...
itemNameStr.postUpdate(avr)

[rlkoshak (Rich Koshak)]

See Design Pattern: Associated Items for a full discussion. But, as rossko57 indicates, the code you have above is trying to use the name of triggeringItem so you already have access to that Item. When later when you postUpdate using itemNameStr, you can use the postUpdate Action.

postUpdate(itemNameStr, avr)

This is one of the few cases where use of the Action is OK.

In those cases where you need the state of an Item where you only have that Item’s name, Olti’s approach is recommended.

Both of these are covered in the Associated Items DP.

[NCO (E. Gerland)]

@rossko57 @Olti

Awesome - thank you for your quick help.
I am going to merge your suggestions as @rlkoshak suggested, because I like the syntax itemNameStr.postUpdate(avr) better.