Out argument on Custom Activity

[Aoshua]

Hello,

I am very excited to incorporate Elsa into my team's software!

I am trying to convert some existing Activities that I have for WF to Elsa, and I have some questions about in-arguments and out-arguments. My activities often take arguments (in-arguments) and return objects and primitives to be used as arguments in the next activity (out-arguments). If I'm understanding this tutorial, I should be able to achieve in-arguments with properties on my activity, but how can I achieve out-arguments? It seems that an OutcomeResult can only be a string with statuses such as Done, True and False?

[tomy2105]

Actually, what you are looking for is OutputResult. And it can be object of any kind.
Your custom activity would returns both OutcomeResult and OutputResult usually combined, something like return Outcome("AnOutput ", someObject).

[Aoshua]

I haven't seen this tutorial yet, but it looks really helpful. Thanks, I'll let you know if I still have any questions afterward 😁

[Aoshua]

Yes! That was massively helpful!

[Aoshua]

Absolutely. The biggest difference will be that instead of writing C# lambda statements as workflow expressions, you’ll be writing them in JavaScript or Liquid, depending on the most appropriate use case.

So in the designer, I have Activity1 which has some output and I have Activity2 that takes some input (with the same type as the output from Activity1). The input property on Activity2 has an ActivityProperty attribute setting the DefaultSyntax = SyntaxNames.JavaScript, but I notice that back in the designer the input is not rendered with Monaco editor. What would I type in the HTML input for this input property, if I was using JavaScript, to get the value from the previous activity? Is there a global JavaScript property that holds the value? Maybe something like context.Input?

[sfmskywalker]

Yeah so the DefaultSyntax is a little bit confusing, it right now it doesn’t affect the default display mode of an activity property editor.

Just make sure that you also supply a list of SupportedSyntaxes so that the UI will give you the option of switching to the JavaScript editor, where you can simply use the input variable.

I’ve done a little bit of work already on support JavaScript expressions here: https://elsa-workflows.github.io/elsa-core/docs/next/expressions/expressions-javascript#input

[Aoshua]

Excellent. Thanks again for the help!

[Aoshua]

For now I will try to get 2.0 running in my project... But does anyone know how to achieve in and out arguments in Elsa 1.x?

[sfmskywalker]

Output.SetVariable("someKey", myObject);
// This at least compiles... Could this be it? (about to go test)

For Elsa 1, that's exactly what you are looking for.
Output there is a dictionary that you can access from the next activity (or any subsequent activities).

For Elsa 2, an activity can currently only return a single output (which can be any type of object as @tomy2105 mentioned), but your comment about Windows WF out-arguments reminded me of that feature, and how it would fit beautifully with Elsa as well. In fact, it would automatically provide a convenient way for the designer to infer what types of output an activity provides, which helps with things like intellisense and output value pickers.

[sfmskywalker]

I created an issue for this.

[Aoshua]

Thanks! That will be a great feature to add to 2.0