Scripting: Invoke Actions from Scripts

Prerequisites

First step is to open the script module, create a new script, and open the script editor. These steps are described in detail here: Writing Scripts.

To get access to the WoT functionality, include the ELCO WoT module by adding this import instruction at the top of the script:

const WoT = require("elco-wot");

Invoking actions

In order to call an action, you can use the InvokeAction method of an exposed or consumed thing.

thing.invokeAction("action_name", [action input]);

The invokeAction method is asynchronous and therefore returns a promise. If you want to make sure that the action has been invoked before resuming execution, add the await keyword:

await thing.invokeAction("action_name", [action input]);

Sometimes, different actions demand different input types. Check the following examples which use the most common inputs:

Empty Value

thing.invokeAction("action_name");

String Input

thing.invokeAction("action_name", "input_value");

Numeric Input

thing.invokeAction("action_name", 123456);

List Input

thing.invokeAction("action_name", ["input_item_1", "input_item_2", "input_item_3"]);

Object Input

thing.invokeAction("action_name", {"input_item": "input_item_value"});

Example script

Here is a full example about how to call actions from scripts. In this example, we will connect to an ELCO RFID Q-Series Reader device and execute a single scan for 10000 milliseconds, everything done via actions. Moreover, we will show the tags which where read during the scanning process.

const WoT = require("elco-wot");

/** Thing fragment to be discovered */
let fragment = {
    title: "AssemblerScanner",
    type: "elco.rfid"
};

/** Discovery object */
let discovery = WoT.discover({
    fragment: fragment
});

/** Main example */
InvokeActionsExample();

async function InvokeActionsExample() {
    /** Discover and consume a thing */
    let consumedThing = await DiscoverAndConsumeThing(discovery);
    if (consumedThing === null) {
        return;
    }
    console.log("Discovered thing: " + consumedThing.getThingDescription().title);

    try {
        /** Observe a property: In this case, we will observe the list of
         * scanned tags, displaying every value update of the mentioned list
         */
        consumedThing.observeProperty("scan", function (newValue) {
            console.log("Scanned tags: " + newValue);
        });

        /** Invoke action connect: If the device is not connected, then
         * this action will establish a new connection with it
         */
        await consumedThing.invokeAction("connect");
        console.log("Invoked action: connect");

        /** Invoke action single_scan: This will execute a scanning process
         * for 10000 milliseconds (10 seconds)
         */
        await consumedThing.invokeAction("single_scan", {"duration": 10000});
        console.log("Invoked action: single_scan (duration: 10000 milliseconds)");
    } catch (err) {
        /** Report an error (if any) */
        console.log("Calling actions error: " + err.message);
        return null;
    }
}

/** Extracted from: Discovering and Consuming Thing
 * more information at:
 * - https://wiki.elco-automation.de/display/I2UM/Discovering+and+Consuming+a+Thing
 */
 async function DiscoverAndConsumeThing(discovery) {
    let thingDescription = {};
    discovery.start();
    do {
        try {
            thingDescription = await discovery.next();
            if (thingDescription !== null) {
                discovery.stop();
            }
        } catch (err) {
            discovery.stop();
            if (err.message === "not found") {
                console.log("Thing not found");
            } else {
                console.log(err.message);
            }
           return null;
        }
    } while (!discovery.done);

    try {
        let consumedThing = await WoT.consume(thingDescription);
        return consumedThing;
    } catch (err) {
        console.log(err.message);
        return null;
    }
}

Output Example

Discovered thing: AssemblerScanner
Invoked action: connect
Invoked action: single_scan (duration: 10000 milliseconds)
Scanned tags:
Scanned tags: E2009A4120010AF000002551
Scanned tags: E2009A4120010AF000002551,E2009A4120010AF000001985