Mapp View eventscript opcua(...).valueChanged not firing if started in typed async class

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1

Hi Community

I’ve written typed classes for OPC variables because I want to be able to spot errors at compile time.
To do this, I’ve written a factory to handle the different variants (OPC-Bool/-Int/etc. & Session-Bool/-Real/etc.).
The class must be async because a data type match is checked at startup (runtime).

If ((typeof await myObject.getValue()) !== usedType) → Exception

Now, a very strange behavior:

  • The ValueChanged event integrated into the classes for the factory fires when I add an additional “opcua(myOpcPath).valueChanged(e => { DoStuff })”
  • If I comment out the additional “<opcUa_EventAction>”, no event fires anymore.

Interpretation:
The B&R JavaScript logic doesn’t recognize when an OPC variable needs to be “activated” at a (relatively low?) nesting depth. The OPC subscriptions are deactivated similarly to when leaving a page.

Example code:

(async () => {
    const opcPath = "::LineCtrl:stGui.BirdViewTransfStr";
    const logger = new Logger('debug');

    opcua(opcPath).valueChanged(e => { console.log('Something happens: ' + e.detail.newValue) } );

    const birdviewTransform = await ValueSourceFactory.fromOpcString(opcPath, logger);

    if (birdviewTransform) {
        logger.info('birdviewTransform was created and will be started.');
        birdviewTransform
            .subscribe(e => console.log('New value:', e))
            .start();
    } else {
        logger.error('ValueSource could not be created (type fault or no OPC variable)');
    }
})();

If the line

opcua(opcPath).valueChanged(e => { console.log('Shit happens: ' + e.detail.newValue) } );

is commented out, then

.subscribe(e => console.log('New value:', e))

will no longer work.

2

Message in console of browser

Error when trying to read the value of node “::LineCtrl:stGui.stConfig.Dummy”: server status: undefined
Subsequent actions are not executed!

This message appears when I test different architectural approaches. The call now looks like this: var birdviewTransform = ValueSourceFactory.fromOpcInt(opcua(opcPath), logger, opcPath);

It is no “async/await” but it looks like using “opcua(..)” in classes (“subsequent actions”) is not allowed by B&R, right? As I understand this message.

This is no typical OPC behavior. Could you offer further options for OPC (e.g. no “automatic closing subscriptions” functionalities which cannot be handled)?

3

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