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Getting the root node from a resource [message #1059808]

Tue, 21 May 2013 13:11

Erick Fonseca
Messages: 26
Registered: December 2011

Junior Member

Is there a specific way to get the root node from a Resource? Currently I'm doing

resource.getContents().get(0)

But I feel it's weird to get the whole content list if I just want the root.

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Re: Getting the root node from a resource [message #1059878 is a reply to message #1059808]

Wed, 22 May 2013 01:14

Henrik Lindberg
Messages: 2431
Registered: July 2009

Senior Member

On 2013-21-05 10:12, Erick Fonseca wrote:
> Is there a specific way to get the root node from a Resource? Currently
> I'm doing
>
> resource.getContents().get(0)
>
>
> But I feel it's weird to get the whole content list if I just want the
> root.

You are doing it right.
A Resource is just more general than the use case of containing a parse
result.

- henrik

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Re: Getting the root node from a resource [message #1059882 is a reply to message #1059808]

Wed, 22 May 2013 01:41

Ed Willink
Messages: 3191
Registered: July 2009

Senior Member

Hi

You're probably also doing

(MyRoot)resource.getContents().get(0)

which means that the user gets to see confusing stack traces for the
following errors
Resource is empty
Resource is multi-rooted
Resource doesn't contain MyRoot
usually resulting from a file name typo, but sometimes through
application defects.

I've taken to coding at least

for (EObject eObject : resource.getContents()) {
if (eObject instanceof MyRoot) {
doSomethingWith((MyRoot)eObject);
}
else {
some error
}
}

Regards

Ed Willink

On 21/05/2013 18:12, Erick Fonseca wrote:
> Is there a specific way to get the root node from a Resource?
> Currently I'm doing
>
> resource.getContents().get(0)
>
>
> But I feel it's weird to get the whole content list if I just want the
> root.

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Re: Getting the root node from a resource [message #1060039 is a reply to message #1059882]

Wed, 22 May 2013 11:20

Hallvard Traetteberg is currently offline

Hallvard Traetteberg
Messages: 539
Registered: July 2009
Location: Trondheim, Norway

Senior Member

On 21.05.13 22.41, Ed Willink wrote:
>
> (MyRoot)resource.getContents().get(0)
>
> which means that the user gets to see confusing stack traces for the
> following errors
> Resource is empty
> Resource is multi-rooted
> Resource doesn't contain MyRoot
> usually resulting from a file name typo, but sometimes through
> application defects.
>
> I've taken to coding at least
>
> for (EObject eObject : resource.getContents()) {
> if (eObject instanceof MyRoot) {
> doSomethingWith((MyRoot)eObject);
> }
> else {
> some error
> }
> }

Yes, this is in general a lot better, since with Xtext-based DSLs it is
common to derive other models, and your particular root may not always
be the first element in such a case. I wish EcoreUtil had a method
<T> T getRoot(Class<T> clazz, boolean throwError) that did this, so it
was easy for everybody to start using this coding style.

Hallvard

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Re: Getting the root node from a resource [message #1060055 is a reply to message #1060039]

Wed, 22 May 2013 13:49

Erick Fonseca
Messages: 26
Registered: December 2011

Junior Member

Thank you for the insights. I will perform this check.

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