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correct downcast from Element to other UML types [message #1848202]

Wed, 24 November 2021 20:57

Ilja Kraval

Messages: 34
Registered: October 2021

Member

Hi all,
I'm a beginner in Acceleo and I can't find a solution for one template:
I have an "anIssue" UML element of type "InstanceSpecification". From it, several "Dependencies" lead to various elements of different types (Class, Property, UseCase, etc.). I need to list their properties, ie perform a treated downcast.
I downcast to subtypes via oclAsType (). It works for me, but I don't know how to handle the correctness of the downcast before it is called and thus avoid "invalid".
I enclose a statement cycle for Dependency with a note where treatment is missing:
-------------------------------------

[for (dep: uml :: Dependency | anIssue.getClientDependencies ())]
[dep.name /]
[comment Missing correctness handling like "If anIssue.Type is Class" /]
Class:
JAVA name = [dep.target.oclAsType (Class) .name /],
ANALYSIS name = [dep.target.oclAsType (Class) .getLabel () /]
[dep.ownedComment._body /]

[comment Next block for "if anIssue.Type is Property" etc. /]
[/ for]

-----------------------------------

Thanks for concrete advice

Ilya

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Re: correct downcast from Element to other UML types [message #1848203 is a reply to message #1848202]

Wed, 24 November 2021 21:11

Ed Willink

Messages: 7379
Registered: July 2009

Senior Member

oclIsKindOf() (NB not oclIsTypeOf()).

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Re: correct downcast from Element to other UML types [message #1848204 is a reply to message #1848203]

Wed, 24 November 2021 21:42

Ilja Kraval

Messages: 34
Registered: October 2021

Member

Hi Ed,
thanks a lot, I have tried that before.

Although the return type of OclIsKindOf() is according to Acceleo / OCL documentation Boolean:

https://wiki.eclipse.org/Acceleo/OCL_Operations_Reference#oclIsKindOf.28_Classifier_typespec_.29_:_Boolean

so this line (according to previous code with loop)

[ if (dep.target.oclIsKindOf (Class)) ]

reports an error:

"Invalid Expression Type: Bag (Boolean) should be Boolean"

I don't understand why this is so?

Regards,

Ilya

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Re: correct downcast from Element to other UML types [message #1848209 is a reply to message #1848204]

Thu, 25 November 2021 06:02

Ed Willink

Messages: 7379
Registered: July 2009

Senior Member

Hi

You provide barely 10% of a repro so I can only guess that at least one of dep or target involve a collection causing a Bag to be used where you and Acceleo expected a Boolean. (OCL's implicit collect can be nice and readable when correctly used, but distinctly confusing when unwanted.)

If you paste you code so that you can use the Complete OCL or OCLinEcore editor or Xtext OCL Console you can use hovertext to determine the type of each term and operator in an expression. This may help you understand it.

Regards

Ed Willink

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Re: correct downcast from Element to other UML types [message #1848235 is a reply to message #1848209]

Thu, 25 November 2021 17:54

Ilja Kraval

Messages: 34
Registered: October 2021

Member

Hi Ed,

your advice to run editor and test the code was very good!

I did a very simple example: I have one InstanceSpecification1 with two Dependency Dep1 and Dep2, one leading to Class Class1 and the other to Activity Activity1. This can be seen in the pictures in the diagram.

Figure Pic1 shows a list of end properties to the output, including a oclIsKindOf (Activity). Everything looks as expected: One Dependency dep (= iteration parameter) has one supplier and one Boolean output true / false.

However, when I put this Boolean expression to the if condition, see Figure Pic2, Acceleo reports an error. And that's strange.

Is there an explanation for this or is it a bug?

Regards
Ilya

Attachment: Pic2.png
(Size: 49.37KB, Downloaded 16 times)
Attachment: Pic1.png
(Size: 52.06KB, Downloaded 12 times)

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Re: correct downcast from Element to other UML types [message #1848239 is a reply to message #1848235]

Thu, 25 November 2021 19:16

Ed Willink

Messages: 7379
Registered: July 2009

Senior Member

Hi

Once again you provide only 10% of a repro. I suggest you read https://wiki.eclipse.org/OCL/ForumNetiquette to see how to ask questions that provoke answers rather than mutual irritation.

Regards

Ed Willink

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