Developing a DSL Abstract Syntax - Eclipse Modeling Project: A Domain-Specific Language Toolkit - page 46

will reuse this set of templates. Then return to Section 3.2.4 and configure the
mindmap.ecore model to use OCL to implement the rootTopics feature.
We can leverage OCL in our model in additional places to provide an imple-
mentation and avoid having to modify our generated code. Let's begin by adding
a method that returns the full set of subtopics for a given Topic .
Finding All Subtopics
Currently, our model has a subtopics reference on each Topic , along with a
method, allSubtopics() , that is intended to return a list of all of a Topic 's
subtopics—that is, its subtopics, all of their subtopics, and so on. All methods
declared in an Ecore model require an implementation to be provided, so we turn
to OCL, where the implementation of this method is trivial, thanks to the non-
standard closure iterator in MDT OCL:
self->closure(subtopics)
We need to add an EAnnotation to the method in our model with Source
equal to http://www.eclipse.org/2007/OCL . A child Details Entry is
added to the annotation with the previous expression as its Value property and
with a Key value of body . When we regenerate our model code, we can see that
our implementation is provided:
/**
* The parsed OCL expression for the body of the
* '{@link #allSubtopics <em>All Subtopics</em>}' operation.
* <!-- begin-user-doc -->
* <!-- end-user-doc -->
* @see #allSubtopics
* @generated
*/
private static OCLExpression<EClassifier> allSubtopicsBodyOCL;
private static final String OCL_ANNOTATION_SOURCE =
"http://www.eclipse.org/2007/OCL";
/**
* <!-- begin-user-doc -->
* <!-- end-user-doc -->
* @generated
*/
public EList<Topic> allSubtopics() {
if (allSubtopicsBodyOCL == null ) {
EOperation eOperation =
MindmapPackage.Literals.TOPIC.getEOperations().get(0);
OCL.Helper helper = OCL_ENV.createOCLHelper();