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[ATL] How to return a null value from a helper [message #490430]

Thu, 08 October 2009 15:49

Tassilo Horn

Messages: 93
Registered: July 2009

Member

Hi all,

I'm doing my first ATL transformation. There's one helper, that should
return the spouse of a given family member if there is one (You see, I'm
extending that Families2Person example).

So here is the code:

--8<---------------cut here---------------start------------->8---
helper context Families!Member def: spouse : Families!Member =
if not self.familyMother.oclIsUndefined() then
self.familyMother.father
else
if not self.familyFather.oclIsUndefined() then
self.familyFather.mother
else
null
endif
endif;
--8<---------------cut here---------------end--------------->8---

So if my member is neither the father nor the mother of a family, then
he has no spouse and I want to return null. But ATL tells me that the
variable null is undefined. So what's the null literal in OCL?

Bye,
Tassilo

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Re: [ATL] How to return a null value from a helper [message #490476 is a reply to message #490430]

Thu, 08 October 2009 18:31

Eclipse User

Originally posted by: j.neveux.netfective.com

Hi Tassilo,

self.familyMother is null so you need to check it this way:

self.familyMother <> OclUndefined

Regards,

Jean

"Tassilo Horn" <thorn@fastmail.fm> a

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Re: [ATL] How to return a null value from a helper [message #490478 is a reply to message #490476]

Thu, 08 October 2009 19:00

Tassilo Horn

Messages: 93
Registered: July 2009

Member

"Jean Neveux" <j.neveux@netfective.com> writes:

Hi Jean,

> self.familyMother is null so you need to check it this way:
>
> self.familyMother <> OclUndefined

I see, and I need to use OclUndefined as return value, too. Then it
works like a charm.

Thanks a lot,
Tassilo

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