Simple default value for undefined variables

Question

It would be nice to be able to assign a value to a variable, ONLY IF it is not already defined, I have some diagrams that I would like to be stand alone, but would also like to inject values into when running (independent of the diagram).

So I would like to assign a value to a preprocessor value ONLY when not specified from a -D command line option, or defined before the diagram was !included in a simple manner (not using a bunch of tricky !if statements).

I suggest a syntax similar to:

$varable ?= "default value"

Comments

it would be equivalent to

!if %not(%variable_exists("$varable"))
!$varable = "default value"
!endif

but less verbose.

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Correct, its just really ugly if there are a bunch of these.

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Not sure why I cannot close this one?

Answer 1

Thanks for the suggestion, that's a nice idea.

So with last beta http://beta.plantuml.net/plantuml.jar , you can have :

http://www.plantuml.com/plantuml/umla/SoWkIImgAStDuNBCoKnELT2rKt3AJrAmKZ3KKr39IynDLIZEo2_DIL58IbL8pIqegUJYubA4IDZRAYWvPoGMvMIcAg7hDiBK3LMAq0_Kxf9Obfc2eTaOKpDO8QhLhYKPYNaOUarmwNL8pKi1UXC0

Is this what you were expecting ?

Comments

That works great!

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Do you need to update any documentation???

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Hello T.,

Yes, of course.
It is done, here:

• https://plantuml.com/preprocessing#788fa5fb2276ed17

Regards,
Th.