Check if a variable has some value

[Ronnie-personal]

I have a quick question.

In Rego language, how to check if a variable has some value and is not undefined?

Thanks.

[srenatus]

default x_is_blah(_) := false
x_is_blah(x) { x == "blah" }

Default function values are a new feature, check your OPA version.

[srenatus]

Actually this is wrong. I'll get back to you when I'm at a computer, if nobody beats me to it.

[Ronnie-personal]

Thanks for the prompt reply. I also need to understand if Rego function supports optional parameter and default return value.

[srenatus]

Try object.get

[Ronnie-personal]

default x_is_blah(_) := false
x_is_blah(x) { x == "blah" }

Default function values are a new feature, check your OPA version.

Indeed, it works in OPA 0.55, excellent.

[Ronnie-personal]

Thank you for the information, very helpful!
One last question, could you confirm whether Rego function supports optional parameter?

[srenatus]

It's not possible -- only via passing objects, as a workaround.