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[QVTO] Nullable enumerations [message #481967]

Mon, 24 August 2009 22:02

Alex Mising name

Messages: 51
Registered: August 2009

Member

Is there any way QVT could directly support EMF/Ecore nullable enumerations pattern? Currently assigning to an attribute using this pattern in QVT requires additional cast of the EnumLiteral being assinged to the "wrapper" EDataType ...

Some background: There appears to be a standard EMF/Ecore pattern for nullable enumerations (enumerations that can have a null value in addition to their enumerated values) - using an additional "wrapper" EDataType as a type for an attribute, linked to the appropriate EEnum via ExtendedMetadata annotation. This patterns is used by XSD-derived Ecore models, and is frequently referred to as pattern of choice for this kind of thing on EMF forums. (The only alternative is to introduce a special NULL EnumLiteral into each nullable enum.)

This should only take a check for relationship between EDataType and enumeration literal for the assignment. Admittedly, this would have to reach into Ecore annotations, which is somewhat unusual I assume for QVT compiler, but the pattern appears to be common enough and important enough to justify supporting it directly...

Thank you,
Alex

[Updated on: Tue, 25 August 2009 00:07]

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Re: [QVTO] Nullable enumerations [message #482154 is a reply to message #481967]

Tue, 25 August 2009 14:21

Eclipse User

Originally posted by: dvorak.radek.gmail.com

Hi Alex,

At the moment there is no direct support for this in QVTO.
Could you please raise bugzilla so we can track this down
https://bugs.eclipse.org/bugs/enter_bug.cgi?product=M2M& component=QVT_OML-Engine

Regards,
/Radek

On Tue, 25 Aug 2009 00:02:26 +0200, Alex <alex.leites@gmail.com> wrote:

> Is there any way QVT could directly support EMF/Ecore nullable
> enumerations pattern? Currently assigning to an attribute using this
> pattern in QVT requires additional cast of the EnumLiteral being
> assinged to the "wrapper" EDataType ...
>
> Some background: There appears to be a standard EMF/Ecore pattern for
> nullable enumerations (enumerations that can have a null value in
> addition to their null values) - using an additional "wrapper" EDataType
> as a type for an attribute, linked to the appropriate EEnum via
> ExtendedMetadata annotation. This patterns is used by XSD-derived Ecore
> models, and is frequently referred to as pattern of choice for this kind
> of thing on EMF forums. (The only alternative is to introduce a special
> NULL EnumLiteral into each nullable enum.)
>
> This should only take a check for relationship between EDataType and
> enumeration literal for the assignment. Admittedly, this would have to
> reach into Ecore annotations, which is somewhat unusual I assume for QVT
> compiler, but the pattern appears to be common enough and important
> enough to justify supporting it directly...
>
> Thank you,
> Alex

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