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[Xpand/Xtend] how to organize templates for multiple output languages [message #500395]

Wed, 25 November 2009 22:01

hoschi

Messages: 6
Registered: November 2009

Junior Member

Hi,

I want to writa a code generator for the targe languages java, C# and C++. I'm not sure how to organize my templates to make it readable and DRY.

First of all I see no possability to call or use another xpand template from a xpand template. I want this to split big template files in more small files and keep it more readable.

My first idea was to set a global var "language" in the workflow file with the name of the target language. Create 3 workflows, for each target language one workflow with the global var set to the language. So the xpand template can hold only the logic and the xtend file can hold the text generation like this example

Xtend

getTargetLang() : ((String)GLOBALVAR language);

buildClassName(String name) :
	switch (getTargetLang()) {
   		case 'java' : 'public class '+name
   		case 'c#' : 'class '+name
   		default : ''
};

Xpand

«EXTENSION template::lib»

«DEFINE main FOR model::DataHolder»
«EXPAND main FOREACH items»  
«ENDDEFINE»

«DEFINE main FOR model::DataA»
«FILE this.name+".dataa"»
«buildClassName(this.name)»
«ENDFILE»	
«ENDDEFINE»

«DEFINE main FOR Object»
«ENDDEFINE»

Feel free to post your ideas Wink

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Re: [Xpand/Xtend] how to organize templates for multiple output languages [message #500402 is a reply to message #500395]

Wed, 25 November 2009 22:29

Miles Parker

Messages: 1341
Registered: July 2009

Senior Member

Hi Hoschi,

I wrote an article a while back on just this issue..

http://milesparker.blogspot.com/2009/04/meta-models-for-arbi trary-targets-iii.html

Some more current examples to take a look at are:

http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.amp/org .eclipse.amp.amf/plugins/org.eclipse.amp.amf.gen/src/model/? root=Modeling_Project
http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.amp/org .eclipse.amp.amf/plugins/org.eclipse.amp.amf.gen/src/metaabm /tmpl/?root=Modeling_Project

And then:

http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.amp/org .eclipse.amp.amf/plugins/org.eclipse.amp.amf.gen.escape/src/ model/?root=Modeling_Project
http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.amp/org .eclipse.amp.amf/plugins/org.eclipse.amp.amf.gen.escape/src/ metaabm/escape/tmpl/?root=Modeling_Project

But the basic idea is to use Aspects. I'd really argue against the idea of using globals and switches -- the whole idea is that you want to be able to mix in new features independently. I'd be happy to go into greater detail if you have more questions about this approach.

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Re: [Xpand/Xtend] how to organize templates for multiple output languages [message #500426 is a reply to message #500402]

Thu, 26 November 2009 05:49

Christian Dietrich

Messages: 14111
Registered: July 2009

Senior Member

Hello,

here some additional hints:

It is no problem at all to call one template (file) from another:

«EXPAND my::templates::TemplateFile::definitionName
        FOR myModelElement»

second you can give additional paramaters to templates

«DEFINE(String language)  main FOR My::Class»
«FILE this.name+".dataa"»
«buildClassName(this.name, language)»
«EXPAND my::templates::TemplateFile::definitionName(language)
        FOR myModelElement»
«ENDFILE»	
«ENDDEFINE»

and pass the parameter from the workflow

<expand value="example::my::template('Java') FOR myModel"/>

so you won't need a global var at all

Need professional support for Xtext, Xpand, EMF?
Go to: https://www.itemis.com/en/it-services/methods-and-tools/xtext
Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: [Xpand/Xtend] how to organize templates for multiple output languages [message #500785 is a reply to message #500395]

Sat, 28 November 2009 17:16

hoschi

Messages: 6
Registered: November 2009

Junior Member

thank you both for the examples und advices. The AOP feature is really cool and in fact the solutiont for my problem.

@Miles
In your article you say that Xtend has also aspects. Do you have a link for an exapmle how to use it? I don't find it in the docu Sad

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