Custom action tags

[Ricardo Morais]

Hi I need some help. 

I tried using scion's executionContext to provide custom action tags to my scxml meta-model, however I  don't have a way to respond to the events. My sandbox has the function postMessage however I can't threat the event received as the image shows. How can I accomplish this.

Thanks, Ricardo Morais.

[Jacob Beard]

Hi,

Can you please post a snippet of your code that illustrates how you are using SCION’s API?

Thank you,

Jake

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<custom.png>

[Jacob Beard]

Also, please see this post, which describes two techniques to expose a global variable to SCION’s execution context:

https://groups.google.com/d/msg/scion-dev/275nXWUyjkM/nRyBDaHmDwAJ

Thank you,

Jake

[Ricardo Morais]

Thanks for the quick response Jake, 

I want to create a new action tag, for example the <logme> tag. However I also want the logme action to be able to receive the event when it is put inside a transition. Like in my previous message the code generated does not send the event through the postMessage function (I define the postMessage in my sandbox to interpret the custom action). 

I also already read the https://groups.google.com/d/msg/scion-dev/275nXWUyjkM/nRyBDaHmDwAJ and I don't want to use the script tag.

I would like to do this in the best way possible, not in a hacky way.

Thanks again, 

Ricardo Morais.

[Ricardo Morais]

I uploaded the same image two times instead of this one, sorry.

[Jacob Beard]

Hi Ricardo,

The code you posted looks like it will successfully install the postMessage function on the global object. You can test that this is working using the <script> tag.

Regarding implementing a custom action tag, there is a specification written for this, but it is not yet implemented. I will revisit this feature soon.

Thanks,

Jake

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[Jacob Beard]

You can track issue #336 "Formalize and expose plugin API for custom actions" here: https://github.com/jbeard4/SCION/issues/336

[Ricardo Morais]

Thanks for the response,

Is there a work around for this for now? I can already make my own actions, all I need is to receive the event. Is it possible for you to make a small patch like the picture shows in the scjson-to-module.js file in the 617 line?

[Jacob Beard]

Yes, the attached patch would work as a workaround. I would recommend forking the SCION repository and posting your code there.

Thank you,

Jake

[Ricardo Morais]

I will try that. Thank you for your time Jake.

[Jacob Beard]

You are welcome. Good luck.

[Ricardo Morais]

Hi Jake,

I have another question regarding the use of custom actions in the SCXML. Is it possible to extract the namespace of the action tag e.g. <ns:test att1=""> (extracting the 'ns')? I already have a fork of the scion library but I don't seem to be able to find how to retrieve the namespace of the tag. Do you have any idea?

Thanks,

Ricardo Morais

[Jacob Beard]

Hi Ricardo,

SCION compiles SCXML to an intermediate JSON format called SCJSON. SCJSON inlines “custom" namespaces (namespaces that are not SCXML or the default namespace) on the action object’s “$type” attribute using the template “{namespaceURI}localName”. This is the same technique used by the python lxml library to handle namespaces.

Previously, this technique was only applied to attributes in custom namespaces, but I have pushed a patch to apply this technique to tags as well: https://github.com/jbeard4/SCION/commit/b814d88d35842b354e84e7211e8797d692e74282

Now, for example, if you do:

    model.prepare(function(err, fnModel){

//start state machine here

    },{

      postMessage : console.log.bind(console,'custom action tag parameters:')

    });

On SCXML:

<scxml xmlns="https://www.w3.org/2005/07/scxml" xmlns:foo="http://foo.com/">

  <state id="A">

    <onentry>

      <foo:bar foo:bat="bif" belt="bin"/>

    </onentry>

  </state>

</scxml>

You will get the following output:

custom action tag parameters: { name: 'Sandbox.action',

  data:

   { '$line': 3,

     '$column': 41,

     '$type': '{http://foo.com/}bar',

     '{http://foo.com/}bat': 'bif',

     belt: 'bin' } }

You might want to use this regex from scjon-to-module.js in your code to parse out the inlined namespace: 

var stripNsPrefixRe = /^(?:{(?:[^}]*)})?(.*)$/;

You can get this change by pulling the master branch into your fork. 

Please let me know if you have any questions about this. Thank you,

Jake

[Ricardo Morais]

Hi Jake,

Thank you so much for your help, I followed your instructions and everything went well. I have another question but I think it is off-topic so I might create a new thread soon.

Best regards,

Ricardo Morais.