Use of define

Question

I'm creating a library and currently using !define like below so that I can control the style and such apart from the layout. The docs state that !define is deprecated and not to use it. How would this be ported to function or procedure. I've tried a few ways and can't get it to work.

@startuml

!define Thing(label) entity label << (T, white) >>
!define SubThing(label, type) <i>label</i> : type

Thing("foo"){
    SubThing("bar", "string")
    SubThing("bar2", "string")
    SubThing("bar3", "object")
}

@enduml

Answer 1

Hello J.,

Here is a simple proposal:

@startuml

!procedure  Thing(label)
entity label << (T, white) >>
!endprocedure

!procedure SubThing(label, type)
<i>label</i> : type
!endprocedure

Thing("foo"){
    SubThing("bar", "string")
    SubThing("bar2", "string")
    SubThing("bar3", "object")
}

@enduml

See also doc. here:

• https://plantuml.com/preprocessing

Regards,
Th.

Comments

Perfect. Thanks. I noticed in the docs that sometimes variables are prepended with $ and sometimes not. They say that it should start with a $ but it seems more of a developer choice. I think when I was trying to make it work, I was using a mix of them. Does the prepended $ really matter? It seems more of a best practice and not required?

---

Does the prepended $ really matter? It seems more of a best practice and not required?

It's more a best practice, and not required.

I'm sure it will bring some confusion but in your case you can also have:

@startuml

!function Thing($label)
!return "entity " + $label + " << (T, white) >>"
!endfunction

!function SubThing($label, $type)
!return "<i>" + $label + "</i> : " + $type
!endfunction

Thing("foo"){
    SubThing("bar", "string")
    SubThing("bar2", "string")
    SubThing("bar3", "object")
}

@enduml

The difference between function and procedure may be difficult to get :-)

---

Yes, it is a best practice...

To avoid... this kind of error:

@startuml
!procedure  Thing(label)
class "label of label is label" << (T, white) >>
!endprocedure

!procedure  Thing2($label)
class "label of label is $label" << (T, white) >>
!endprocedure

Thing("foo")
Thing2("foo")
@enduml

Regards,
Th.

---

To continue PlantUML's answer...

In your case you can also have, function on one-line :

@startuml
!function Thing($label) !return "entity " + $label + " << (T, white) >>"

!function SubThing($label, $type) !return "<i>" + $label + "</i> : " + $type

Thing("foo"){
    SubThing("bar", "string")
    SubThing("bar2", "string")
    SubThing("bar3", "object")
}
@enduml

Enjoy,
Regards.

---

Yeah. Make sense. Having the $ within the library itself makes sense as a good practice. What I wasn't wanting is requiring it from the end user perspective, like below, where its prepended to the instantiation.

$Thing("foo"){
    $SubThing("bar", "string")
    $SubThing("bar2", "string")
    $SubThing("bar3", "object")
}

Thanks all for the help.