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navigating inverse of references? [message #804629]

Wed, 22 February 2012 20:51

Scott Finnie

Messages: 94
Registered: October 2011

Member

Apologies, am sure this must be answered somewhere but can't find it.

Is there an easy way to navigate the inverse of a reference?

For example (from tutorial):

Feature:
  many?='many'? name = ID ':' type = [Type]
;

given an instance f1 of Feature, the type is accessible as f1.getType(). But what about the other way? i.e. given an instance of Type, how to find all Features that use it?

Thanks.

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Re: navigating inverse of references? [message #804652 is a reply to message #804629]

Wed, 22 February 2012 21:25

Alex Tugarev

Messages: 14
Registered: July 2011

Junior Member

Hi,

you can use the index for this kind of tasks. Have a look at the following snippet.

@Inject protected ResourceDescriptionsProvider resourceDescriptionsProvider;

Resource elementResource = element.eResource();

IResourceDescriptions resourceDescriptions = resourceDescriptionsProvider.getResourceDescriptions(elementResource);
IResourceDescription resourceDescription = resourceDescriptions.getResourceDescription(EcoreUtil2.getURI(element));
Iterable<IReferenceDescription> referenceDescriptions = resourceDescription.getReferenceDescriptions();

for (IReferenceDescription referenceDescription : referenceDescriptions) {
	// set a breakpoint here and inspect "referenceDescription" in debugger
}

Regards,
Alex

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Re: navigating inverse of references? [message #805126 is a reply to message #804652]

Thu, 23 February 2012 11:07

Scott Finnie

Messages: 94
Registered: October 2011

Member

Alex, thanks for the reply. Tried your suggestion but getting NPE on call to eResource().
Here's the code:

@Test
public void testFindInverse() {
	Class cls = OoaFactory.eINSTANCE.createClass();
	cls.setName("TheClass");
	Domain domain = OoaFactory.eINSTANCE.createDomain();
	domain.setName("TheDomain");
	domain.getElements().add(cls);

	Resource elementResource = cls.eResource();
	ResourceDescriptionsProvider resourceDescriptionsProvider = new ResourceDescriptionsProvider();
	IResourceDescriptions resourceDescriptions = resourceDescriptionsProvider.getResourceDescriptions(elementResource);
	IResourceDescription resourceDescription = resourceDescriptions.getResourceDescription(EcoreUtil2.getURI(cls));
	Iterable<IReferenceDescription> referenceDescriptions = resourceDescription.getReferenceDescriptions();
		
	for (IReferenceDescription referenceDescription : referenceDescriptions) {
		@SuppressWarnings("unused")
		int hashcode = referenceDescription.hashCode();
		// set a breakpoint here and inspect "referenceDescription" in debugger
	}	
}

Just getting to grips with EMF/xtext APIs so not very familiar with them. Wonder if it's something to do with running as unit test?

Thanks,
Scott.

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