Doru I think that what I want this is graph traversal that I can specialize and the state of the traversing action should be stored into the model so in a visitor.
Stef
On Sep 21, 2008, at 1:04 PM, Tudor Girba wrote:
It's not that I do not know what a visitor is, I was just curious of the use case, given that we have done quite a bit of things without one :).
I believe that most Visitors can be nicely implemented using class extensions. Of course, when you have a tree and a very complex algorithm with many variation points, then having a visitor does improve the situation. But even then, there is no reason for not exposing the service as an extension method that then calls the visitor. This makes life much easier for the client because there is no need to know how to instantiate the visitor.
Cheers, Doru
On Sep 21, 2008, at 12:44 PM, Stéphane Ducasse wrote:
Yes exactly and I would like to use the importingContext of specify how to filter the model but in a conistent manner.
Stef
On Sep 21, 2008, at 11:33 AM, Oscar Nierstrasz wrote:
Well, if a visitor has to implement many visit methods, but not all visitors need to do something for visitable items, then it is handy to have a default visitor that implements all the visit methods with empty bodies. You then simply subclass this default visitor and override the few visit methods that you need.
There is an example in the compiler construction course.
https://www.iam.unibe.ch/scg/svn_repos/Lectures/CompilerConstruction/04Parsi...
https://www.iam.unibe.ch/scg/svn_repos/Lectures/CompilerConstruction/Example...
Cheers,
- on
On Sep 20, 2008, at 23:33, Tudor Girba wrote:
I am curious about the use case. Could you elaborate a bit on this one?
Cheers, Doru
On Sep 18, 2008, at 1:18 PM, Oscar Nierstrasz wrote:
I guess you mean a default visitor with empty visit methods that can be subclassed?
Yeah, we need that.
- on
On Sep 18, 2008, at 13:09, stéphane ducasse wrote:
Hi guys
We are looking for a model walker (visitor). Does any one of you already implement one?
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