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[Xtext] Default values for optional assignments? [message #468198] Tue, 04 August 2009 09:44 Go to next message
Hauke Fuhrmann is currently offline Hauke Fuhrmann
Messages: 319
Registered: July 2009
Senior Member
Dear xtext folks,

is there a way to specify default values for attribute assignments that
are optional?

Like in:

Node:
(attr=INT)? name=ID

If one omits the INT token, then attr will be initialized with 0 as I
understand. Is there a way to set this default value to some other value?

Cheers,
HAuke

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Re: [Xtext] Default values for optional assignments? [message #468219 is a reply to message #468198] Tue, 04 August 2009 10:56 Go to previous messageGo to next message
Sebastian Zarnekow is currently offline Sebastian Zarnekow
Messages: 2788
Registered: July 2009
Senior Member
Hi Hauke,

please have a look at the post processing hook for the meta model
generation. The documentation can be found at http://www.xtext.org. The
FAQ provides an entry point for this one, too:
http://wiki.eclipse.org/Xtext/FAQ#How_can_I_control_the_Xtex t_meta_model_inference_.3F

Hope that helps,
Sebastian
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Am 04.08.2009 15:44 Uhr, schrieb Hauke Fuhrmann:
> Dear xtext folks,
>
> is there a way to specify default values for attribute assignments that
> are optional?
>
> Like in:
>
> Node:
> (attr=INT)? name=ID
>
> If one omits the INT token, then attr will be initialized with 0 as I
> understand. Is there a way to set this default value to some other value?
>
> Cheers,
> HAuke

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Re: [Xtext] Default values for optional assignments? [message #985906 is a reply to message #468219] Fri, 16 November 2012 11:00 Go to previous messageGo to next message
Christopher Brind is currently offline Christopher Brind
Messages: 9
Registered: October 2011
Junior Member
Hi,

I am trying to work this out as well. I see this post is quite old now so I wonder if that FAQ is still accurate? I can't find the things it is referring to in my IDE.

Any help assigning default values to optional grammar would be appreciated.

Cheers,
Chris

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Re: [Xtext] Default values for optional assignments? [message #985922 is a reply to message #985906] Fri, 16 November 2012 11:56 Go to previous messageGo to next message
Christian Dietrich is currently offline Christian Dietrich
Messages: 4399
Registered: July 2009
Senior Member
hi,

IXtext2EcorePostProcessor is still there. it ships with one impl (XtendXtext2EcorePostProcessor)
you may need to install a complete xpand sdk the get full useage of the ide features described in the faq.
or you implement it yourself e.g. as i described it here http://christiandietrich.wordpress.com/2011/07/22/customizing-xtext-metamodel-inference-using-xtend2/

~Christian

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Re: [Xtext] Default values for optional assignments? [message #985923 is a reply to message #985922] Fri, 16 November 2012 12:03 Go to previous messageGo to next message
Christopher Brind is currently offline Christopher Brind
Messages: 9
Registered: October 2011
Junior Member
Thanks Christian, I had just started reading your blog post.

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Re: [Xtext] Default values for optional assignments? [message #986747 is a reply to message #985923] Wed, 21 November 2012 09:19 Go to previous messageGo to next message
Christopher Brind is currently offline Christopher Brind
Messages: 9
Registered: October 2011
Junior Member
Hi again,

Your blog post helped in that I got to the point where I realised that for that particular problem I could just set the default value literal of the attribute.

The problem I have now is that I need to override the getter of an attribute so that if the attribute is null i return a value derived from one of the other attributes.

Obviously I can't just add an operation to override the getter as that invalidates the genmodel, so I'm a little stuck... any suggestions?

Thanks in advance.

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Re: [Xtext] Default values for optional assignments? [message #986803 is a reply to message #986747] Wed, 21 November 2012 12:06 Go to previous messageGo to next message
Christian Dietrich is currently offline Christian Dietrich
Messages: 4399
Registered: July 2009
Senior Member
Hmmm i have actually no idea for that. Maybe you have to switch to a
manually maintained metamodel

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Re: [Xtext] Default values for optional assignments? [message #986806 is a reply to message #468198] Wed, 21 November 2012 12:22 Go to previous message
Christopher Brind is currently offline Christopher Brind
Messages: 9
Registered: October 2011
Junior Member
Drat, that's a shame. Thanks for your reply anyway.

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