How to add a variable to a Rest Message's Content field dynamically?

[Nisar2]

I've a rest message function defined with some default variables:

So via script, I can substitute those values

var rm = new sn_ws.RESTMessageV2('dummyAPI', 'post');
rm.setStringParameter('callback_url', 'xxxxxxxx');
rm.setStringParameter('correlationId', 'yyyyyyy');

But is it possible to add an extra variable and substitute it on the fly? Something like below:

rm.setStringParameter('new_variable', 'abc');

I tried with the above code, but in the scripted rest API resource, when I did

gs.log(JSON.stringify(request.body.data));

I could only see "callbackUrl" and "correlationId" keys and not "new_variable".

Is there way to have that added? I don't want to update the rest message's "Content" field and would like to have that extra variable added by script.

[Geoff_T]

In what scenario would you need an extra variable added. Surely the request body would be pre-defined with mandatory / mandatory values?

[Nisar2]

Dev vs Prod. When triggering in dev environment, I need to add an extra variable for aiding quick testing but when it's pushed to prod the variable is not required. I can simply use instance_name sys_property to know which environment the code is running in. But the only thing I need to know if it's possible to do this.

[Geoff_T]

I'd probably just create separate REST messages. One for Prod, the other non Prod. Then you can call whichever one you want based on the instance_name.

var env = gs.getProperty('instance_name');
var restMessage = env == 'prod' ? 'dummyAPIProd' : 'dummyAPINonProd';

var rm = new sn_ws.RESTMessageV2(restMessage, 'post');
rm.setStringParameter('callback_url', 'xxxxxxxx');
rm.setStringParameter('correlationId', 'yyyyyyy');

if(env == 'prod')
rm.setStringParameter('new_variable', 'abc');

[Nisar2]

Yes, this is a solution that we had already considered. But your answers seem to suggest I cannot do this via script?