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How do I restrict changes to the model based on attribute values? [message #148479]

Thu, 30 August 2007 04:51

Eclipse User

Hi,

I 'm not sure how to achieve the following goal with GMF: I want to render
my nodes uneditable based on an attribute value. But not every kind of
change should be forbidden. So, for example, my node mustn't be the target
of a new connection but can be the source. How do I achieve this?

I played around with the approveRequest-Method of a subclass of
AbstractEditHelperAdvice but ran into the difficulties with the
StackOverflow (see other thread). Is this the right way to achieve my goal
or are there other suggestions?

Greetings,
Alexander

Re: How do I restrict changes to the model based on attribute values? [message #148776 is a reply to message #148479]

Mon, 03 September 2007 04:30

Eclipse User

Hi Alexander!
> So, for example, my node mustn't be the target of a new connection
> but can be the source. How do I achieve this?

I think a link constraint using OCL may work. (Add a "Link
Constraints" to your "Link Mapping" and then add a "Source End
Constraint" or a "TargetEnd Constraint".)

For example I used it while metamodeling an Activity Diagram. I want
theinitial node only having one outgoing connection and no incoming
connections.

For only one outgoing connection I set the Source End Constraint
to:self.outgoing->size() = 0
My initial node is an EClass in my metamodel. "outgoing" is an
EReferenceof it which has the lower bound 0 and the upper bound -1.

For no incoming connections I set the Target End Constraint to:
not self.oclIsTypeOf(InitialNode)
"InitialNode" is the actual name of the EClass in my metamodel.

To answer your question you also can access any EAttribute. For
example if you want to enable creating an incoming connection only if
a boolean attribute of the target node is set to true then use the
following OCLstatement as the Target End Constraint:
self.myBoolean = true
If you also have to check the type of the target EClass because you
link can connect to different node types then
use:self.oclIsTypeOf(myNodeTypeOfInterest) implies self.myBoolean =
true

Hope that helps.
Nicolai

--

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You can download it at http://www.malcom-mac.com/nemo

Re: How do I restrict changes to the model based on attribute values? [message #149453 is a reply to message #148776]

Fri, 07 September 2007 05:35

Eclipse User

Hi Nicolai,

yes that was very helpful, thank you! Now the creation is not possible when
I dissallow it.

But as far as I understand does this only work for creating connections.
What can I do to disallow deleteing connections and nodes?

Greetings,
Alexander

"Nicolai Kamenzky" <kamenzky@inf.fu-berlin.de> schrieb im Newsbeitrag
news:nemoMon090307101025@news.eclipse.org...
> Hi Alexander!
>> So, for example, my node mustn't be the target of a new connection
>> but can be the source. How do I achieve this?
>
> I think a link constraint using OCL may work. (Add a "Link
> Constraints" to your "Link Mapping" and then add a "Source End
> Constraint" or a "TargetEnd Constraint".)
>
> For example I used it while metamodeling an Activity Diagram. I want
> theinitial node only having one outgoing connection and no incoming
> connections.
>
> For only one outgoing connection I set the Source End Constraint
> to:self.outgoing->size() = 0
> My initial node is an EClass in my metamodel. "outgoing" is an
> EReferenceof it which has the lower bound 0 and the upper bound -1.
>
> For no incoming connections I set the Target End Constraint to:
> not self.oclIsTypeOf(InitialNode)
> "InitialNode" is the actual name of the EClass in my metamodel.
>
> To answer your question you also can access any EAttribute. For
> example if you want to enable creating an incoming connection only if
> a boolean attribute of the target node is set to true then use the
> following OCLstatement as the Target End Constraint:
> self.myBoolean = true
> If you also have to check the type of the target EClass because you
> link can connect to different node types then
> use:self.oclIsTypeOf(myNodeTypeOfInterest) implies self.myBoolean =
> true
>
> Hope that helps.
> Nicolai
>
> --
> I'm trying a new usenet client for Mac, Nemo OS X.
> You can download it at http://www.malcom-mac.com/nemo
>

Re: How do I restrict changes to the model based on attribute values? [message #149899 is a reply to message #149453]

Tue, 11 September 2007 04:33

Eclipse User

Hi Alexander,

did you find a way prohibiting the deletion of nodes?

I currently face the same problem.

By the way:
The constraints I posted before I learnt from
< http://www.sts.tu-harburg.de/pw-and-m-theses/2006/dorai06.pd f>
It's a good thesis on many different kinds of constraints.
But as I know a constraint can't prohibit deleting a node or a link.

Cheers,
Nicolai

--

I'm trying a new usenet client for Mac, Nemo OS X.
You can download it at http://www.malcom-mac.com/nemo

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