how to move field to another typeDeclaration

[Frederik Schmidt]

Hi recoder developers,

I would like to write a transformation to move a field from one
typeDeclaration to another. Its no problem to erase a field from one type
declaration. However, im struggeling to add the field in another
typeDeclaration. See the code snippet for current attempt below. Based on the
transformation tutorial i would need a statementBlock to attach the field.
unfortunately, im not able to retrieve a StatementBlock from the available
TypeDeclaration to attach the field.

Maybe someone can give a hint how to solve this issue.

private void addField(TypeDeclaration targetTypeDeclaration, Field field)
{
List<Field> allFields = targetTypeDeclaration.getAllFields();
allFields.add(field); // certainly this doesnt write back into the definition
of the typeDeclaration.
CrossReferenceServiceConfiguration crsc =
CrossReferenceServiceConfigurationFactory.getInstance();
ChangeHistory changeHistory = crsc.getChangeHistory();
ProgramElement pElement = (ProgramElement) field;
changeHistory.attached(pElement);
}

regards
Frederik

[Tobias Gutzmann]

Hi,

There are two issues:
1) A "field" is never attached to a StatementBlock, but to a TypeDeclaration.
Only "local variables" can be attached to statement blocks.
2) There's an essential difference between a general "Field" and a
"FieldDeclaration" (this generailizes to other members as well). A "Field"
can, e.g., also be a "FieldInfo" as retrieved from bytecode; recoder does not
refactor bytecode. A "FieldDeclaration" is a field that is present in the AST,
i.e., in the analyzed source code.
Now, "getAllFields()" also returns a List also including inherited fields.
What you are looking for is "getFields()", which returns an ASTList. An
ASTList is part of the AST; changes to it are reflected in the AST.

What you probably are looking for is this (warning: untested, I leave that to
you :))
private void addField(TypeDeclaration targetTypeDeclaration, Field field) {
ASTList<Field> fields = targetTypeDeclaration.getFields();
fields.add(targetTypeDeclaration.getProgramFactory().createFieldDeclaration(..
.);
// rest as you wrote it...
}

You will have to provide proper arguments to createFieldDeclaration(). The
following constructor should be present (again, I didn't test it as I don't
have recoder at hand right now):
pf.createFieldDeclaration(TypeKit.createTypeReference(field.getType()),
field.getName());

Let me know if you have any further questions.

Best regards,
Tobias

[Frederik Schmidt]

Hi Tobias,

thanks for your help... Below a code snipped including your hints, which
enabled me to move a field to a given type declaration. Its certainly not
perfect, but for now it does the job:-) Thanks again

cheers
frederik

private void addFieldToTypeDeclaration(TypeDeclaration targetTypeDeclaration,
Field field)
{
FieldSpecification fieldSpecification = (FieldSpecification) field;

ASTList<DeclarationSpecifier> declarationSpecifiers =
fieldSpecification.getDeclarationSpecifiers();
JavaProgramFactory factory = targetTypeDeclaration.getFactory();

FieldDeclaration parent = fieldSpecification.getParent();
TypeReference typeReference = parent.getTypeReference();

FieldDeclaration fieldDeclaration = factory.createFieldDeclaration();

fieldDeclaration.setDeclarationSpecifiers(declarationSpecifiers);
fieldDeclaration.setFactory(factory);
fieldDeclaration.setMemberParent(targetTypeDeclaration);
fieldDeclaration.setTypeReference(typeReference);

ASTArrayList<FieldSpecification> fieldSpecifications = new
ASTArrayList<FieldSpecification>();

fieldSpecification.setParent(fieldDeclaration);
fieldSpecifications.add(fieldSpecification);
fieldDeclaration.setFieldSpecifications(fieldSpecifications);

ASTList<MemberDeclaration> members = targetTypeDeclaration.getMembers();
members.add(0, fieldDeclaration);

CrossReferenceServiceConfiguration crsc =
CrossReferenceServiceConfigurationFactory.getInstance();
ChangeHistory changeHistory = crsc.getChangeHistory();
ProgramElement pElement = (ProgramElement) fieldDeclaration;
changeHistory.attached(fieldSpecification);
changeHistory.attached(pElement);

}

[Tobias Gutzmann]

Hi,

If you somehow can guarantee that a FieldDeclaration has only one
FieldSpecification, it can be done much easier because you can just move/clone
the FieldDeclaration (examples for a FieldDeclaration with two
FieldSpecifications: int a, b; -- it makes source code transformations in
general much more complicated...):
In this case you can just deepClone() the FieldDeclaration (note: it's
always better to deepClone() than reusing an AST object, for defensive
programming reasons...)

TypeDeclaration from = ...;
TypeDeclaration to = ...;
FieldDeclaration fd = ...;
FieldDeclaration replFd = fd.deepClone();
int idx = from.getChildPositionCode(fd);
from.replaceChild(fd, null);
to.getMemberDeclarations().add(replFD);
to.makeRoleValid();
sc.getChangeHistory().detached(fd, idx);
sc.getChangeHistory().attached(replFD);

(Again, I haven't actually executed the code above...)

Best regards,
Tobias