Eclipse Community Forums: TMF (Xtext) » When to use XExpression, XblockExpression and just plain parser rule

Home » Modeling » TMF (Xtext) » When to use XExpression, XblockExpression and just plain parser rule

When to use XExpression, XblockExpression and just plain parser rule [message #1736257]

Mon, 27 June 2016 18:57

Eclipse User

I have been prototyping and playing with xText/Xbase for few weeks. I am still lost as there are many components in the system that I have not seen.

Now, I would to understand when to use an XExpression, and when not use it. And if I need an expression, why not use XBlockExpression.

So what factors others use to decide if they need to use an expression or not.

Re: When to use XExpression, XblockExpression and just plain parser rule [message #1736267 is a reply to message #1736257]

Tue, 28 June 2016 03:01

Eclipse User

Usually DSLs won't make any restriction on the kind of expression they allow at a certain position, so XExpression is often right. But if you would like to force that an expression has to be encapsulated in curly brackets, you go with XBlockExpression. For example, if you would like something like an Operation which has a Body, as seen in the Domainmodel example.

As always, it depends...

Re: When to use XExpression, XblockExpression and just plain parser rule [message #1736293 is a reply to message #1736267]

Tue, 28 June 2016 05:53

Eclipse User

Karsten,
Thank you a lot.
I understand that XExpression can be created any where. But when do I use

MyElement returns XExpression:
{MyElement} ......

And when to use

MyElement:
{MyElement} .......

Thank you

Re: When to use XExpression, XblockExpression and just plain parser rule [message #1736302 is a reply to message #1736293]

Tue, 28 June 2016 06:29

Eclipse User

MyElement returns XExpression makes your expression an xexpression so that

- it can be used as initializer of a field or a body of a method, can be handled by typecomputer etc.

MyElement:
{MyElement}

does not

Previous Topic:	[Xtext] NPE in ResourceDescriptionsProvider.createResourceDescriptions() after update to 2.9 / 2.10
Next Topic:	Xtext grammar

Goto Forum:

-=] Back to Top [=-

Current Time: Thu Sep 18 15:12:40 EDT 2025

.:: Contact :: Home ::.

Breadcrumbs

Sign up to our Newsletter