Applying D(on't) R(epeat) Y(ourself) in PlantUML

Question

I'd like to take my code from this:

app_1 .d. lb_fe_port8200
app_2 .d. lb_fe_port8200
app_3 .d. lb_fe_port8200
app_4 .d. lb_fe_port8200
app_5 .d. lb_fe_port8200
 

to something like this:

!procedure $make_clients($clients)
  !while $clients!=0
    app_$clients .d. lb_fe_port8200
    !$clients = $clients - 1
  !endwhile
!endprocedure

$make_clients(5)

However, I get this error:

    app_$clients .d. lb_fe_port8200

Syntax error?

I've tried various approaches to make the parser happy, like saying "app_[$clients] .d. lb_fe_port8200" but while that resolves to a number (I can see the number in the error message like "app_[5] .d. lb_fe_port8200") it is still a syntax error.

Any help appreciated! :) Cheers.

Answer 1

To concatenate a string and a variable you need to use the ## operator:

@startuml
!procedure $make_clients($clients)
  !while $clients!=0
    app_##$clients .d. lb_fe_port8200
    !$clients = $clients - 1
  !endwhile
!endprocedure

$make_clients(5)
@enduml

Comments

OOOH! That looks great, I'll give this a shot. Thank you @Martin! :)

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Ooh, almost to perfection - but can I specify adding leading zeros (aka padded zeros)?

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There's no number formatting function that I'm aware of, so you'll have to roll your own:

@startuml
!function $right($t, $n)
!return %substr($t, %strlen($t) - $n, $n)
!endfunction

!function $pad($x, $y)
!return $right("00000"+%string($x), $y)
!endfunction

!procedure $make_clients($clients)
  !while $clients>=0
    %string("app_"+$pad($clients, 3)) .d. lb_fe_port8200
    !$clients = $clients - 5
  !endwhile
!endprocedure

$make_clients(10)
@enduml

 

Interestingly the "##" trick didn't seem to work on a function result...so I had to use %string(a+b) instead.

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Thank you once again, @Martin. While this is useful for me, I think this will be even more useful to the poor sod that has to accomodate something like 100+ interconnected devices or other objects with PlantUML. :)