Toggle action to dynamically determined action item in oh-repeater

Add-ons UIs
1

I am trying to define a custom widget which displays all items on a group using oh-repeater. If user clicks one of the displayed items it should change the state of a different item which name is built based on the clicked item and the suffix “_Ack”.
I tried different thing but always ending up in a message that their is an illegal character in the path. How do I construct the action item name, so that it works?

2023-03-23 14:55:14.879 [WARN ] [org.eclipse.jetty.server.HttpChannel] - /rest/items/[object%20Object]
java.lang.IllegalArgumentException: Illegal character in path at index 34: http://openhabian:8080/rest/items/[object%20Object]

Code of the widget:

uid: alarm_sensors
tags:
  - in test
  - in use
props:
  parameters:
    - description: Title
      label: Title Text
      name: title
      required: false
      type: TEXT
    - description: Icon to show
      label: the icon
      name: icon
      required: false
      type: TEXT
    - context: item
      description: An item to control
      label: The Group Item
      name: item
      required: false
      type: TEXT
  parameterGroups: []
timestamp: Mar 23, 2023, 11:29:39 AM
component: f7-card
config:
  title: =props.title
slots:
  default:
    - component: oh-list
      slots:
        default:
          - component: oh-repeater
            config:
              fragment: true
              for: i
              sourceType: itemsInGroup
              groupItem: =props.item
            slots:
              default:
                - component: oh-list-item
                  config:
                    icon: =props.icon
                    iconColor: '=items[loop.i.name].state === "ON" || items[loop.i.name].state > 0 ? "green" : "gray"'
                    title: =loop.i.label
                    item: =loop.i.name
                    badge: =(loop.i.state == "ON")?(items[loop.i.name + "_Ack"].state ==='ON'?"Ack":"Alarm"):"OK"
                    badgeColor: =items[loop.i.name + "_Ack"].state ==='ON'?"orange":(loop.i.state == "ON"?"red":"green")
                    action: toggle
                    actionCommand: ON
                    actionCommandAlt: OFF
                    actionItem: '=items[loop.i.name + "_Ack"]'
2

actionItem takes a string of the item name only. When you use items[....] you are using the item name to retrieve an object that contains information about the item’s state. What you want is just the part between the brackets:

actionItem: =loop.i.name + "_Ack"
3

Works! Thanks!