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Dynamic creation of EObject [message #1773030]

Wed, 20 September 2017 12:25

Geoffry Roberts

Messages: 52
Registered: July 2016

Member

I found this bit of code on SO on how to create an EObject programatically:

EClass eClass = EcoreFactory.eINSTANCE.createEClass();
eClass.setName("Interaction1");
eClass.setInterface(true);
EObject obj = EcoreUtil.create(eClass);

When run it throws an NPE because EClass dosen't have a package. From EcoreUtil:

  public static EObject create(EClass eClass)
  {
    return eClass.getEPackage().getEFactoryInstance().create(eClass);
  }

There is in EClass getEPackage() but no setter.

How does the package get set?

btw,
The class I am trying to instantiate is generated and on the classpath.

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Re: Dynamic creation of EObject [message #1773035 is a reply to message #1773030]

Wed, 20 September 2017 14:27

Didier Vojtisek

Messages: 23
Registered: July 2009

Junior Member

Hi

about the way to set the EPackage this is because you must set the reference the other way round: create the EPackage

EPackage pack = EcoreFactory.eINSTANCE.createEPackage();
pack.setName("something'); 
pack.setNsURI("something');

then use the .getEClassifiers().add()

EClass eClass = EcoreFactory.eINSTANCE.createEClass();
eClass.setName("Interaction1");
eClass.setInterface(true);
pack.getEClassifiers().add(eClass);
EObject obj = EcoreUtil.create(eClass);

However, except if this is on purpose (for example if you want to create both the metamodel and model completely dynamically), I think you should not try to recreate you metamodel in order to instantiate model elements.

You should probably consider retrieving the package in the registry,

EPackage.Registry.INSTANCE.getEPackage(YourMetamodelPackage.eNS_URI)

then find you class in the package (navigate in the Eclassifiers and search the one with the expectec name) and instanciate it.

a look to the ecore diagram may help ;-) http://download.eclipse.org/modeling/emf/emf/javadoc/2.9.0/org/eclipse/emf/ecore/doc-files/EcoreRelations.gif

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