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EMF + Multiple inheritance with Interfaces [message #1826794]

Thu, 30 April 2020 15:37

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Given an Interface-EClass (abstract=true, interface=true) A
and an EClass B
Then for a second EClass C with Supertypes A + B

in the generated code CImpl wont inherit from BImpl

if C is with Supertypes B + A it will

is this a feature? or a bug?

for me it was at least a nice pitfall with custom impls in the Impl classes that suddenly got lost ;)

<?xml version="1.0" encoding="UTF-8"?>
<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore" name="demo" nsURI="http://eclipse.org/demo" nsPrefix="demo">
<eClassifiers xsi:type="ecore:EClass" name="SomeInterface" abstract="true" interface="true"/>
<eClassifiers xsi:type="ecore:EClass" name="SomeClass"/>
<eClassifiers xsi:type="ecore:EClass" name="SomeSubclass" eSuperTypes="#//SomeInterface #//SomeClass"/>
</ecore:EPackage>

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: EMF + Multiple inheritance with Interfaces [message #1826801 is a reply to message #1826794]

Thu, 30 April 2020 17:55

Ed Willink

Messages: 7655
Registered: July 2009

Senior Member

Hi

From a pure modeling perspective it's probably a bug that runs into a Java limitation so for Java it's a feature.

When I hit the problem a few years go, I recall concluding that a smarter EMF genmodel might create more problems than the manual workarounds.

If you ensure that the most complicated inherited code is in the first superClass, you reduce the complexity of what you have to clone for the unsupported extra interfaces. You can perhaps share this in shared helper functions to avoid code drift.

If you wrap your Java code up as EAnnotation bodies, the auto-generation should spit the embedded Java out as many times as necessary.

Similarly if you use OCLinEcore (or I guess Xcore) to define the bodies that too should be multiply generated.

Regards

Ed Willink

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