Re: [xwiki-devs] why hasn't the class deletion been implemented?

We have thought about the capability of having class heritage.. but it's not so easy to implement.. Want to work on it ?

Ludovic Pascal Voitot wrote: > ok I see > But do we agree that we shall have a class/mechanism deletion > somewhere? (in fact I agree with myself about that at least because > I'm frustrated not to be able to delete the classes I don't need > anymore :)) > > I'm not sure about something: did you intend to give to the concept of > "class" about the same "generic" extend as the concept of "class" in > any OO language? Is a class a kind of descriptor of entities with > their own properties and relations to other entities? or is a class > only a convenience for gathering properties and creating objects with > these properties? > If XWiki classes are real classes (I think they are) then it would be > nice to push the concepts as far as possible... Moreover, with XE > (that I don't have installed yet), it would be nice to be able to > manage classes directly and to have refactoring features :)... > > Pascal > > > On Tue, Mar 18, 2008 at 12:52 PM, Ludovic Dubost &lt;ludovic(a)xwiki.org > <mailto:ludovic@xwiki.org>> wrote: > > > Yes but we need tons of warning in case properties are deleted. > If class are deleted this is even more problematic as this can make a > lot of deletion. > > For versioning, what we do is we store in the XML of each object the > definition of the class at the time the object was saved. This > means we > can build the class as it was before we actually load the object. > > Now I'm pretty sure we don't really make use of that. > > Ludovic > > Pascal Voitot wrote: > > That's what I think... > > In a ideal world, removing a class or a property should imply > removing > > associated instances naturally... > > Another idea...One question: are classes and properties versioned as > > documents? I mean, if you modify a class, is it possible to keep the > > previous version and keep existing objects as instantiations of the > > older version and then new objects will be instantiations of the > newer > > version of the class? We could also propose an object to be > > translated into the newer version with some risks. > > In this case, it could be simple to modify or remove properties of a > > class even if it would bring some complexity also... > > Then the last problem would be class deletion which would be more > > violent and would need some strong warnings because objects would be > > deleted definitely... in this case, a kind of temporary bin > could be > > interesting... > > > > Pascal > > > > On Tue, Mar 18, 2008 at 10:56 AM, Sergiu Dumitriu > &lt;sergiu(a)xwiki.com <mailto:sergiu@xwiki.com> > > <mailto:sergiu@xwiki.com <mailto:sergiu@xwiki.com>>> wrote: > > > > Pascal Voitot wrote: > > > This might seem stupid but what are the limitations in > class/object > > > deletion? > > > > > > > We don't know what to do with the data. Adding a property is > simple, > > existing objects will not have a property and it will be added > > when the > > object is saved. But when you delete a property, what do we do? > > Leave it > > there? Delete it from all the objects? > > > > If we keep it there, it will be "shadowed", as the > persistence layer > > will not know that it exists. More, if we add back that > property with > > the same name and another type, we'll have errors because we'll > > have two > > instances with the same identifier in two places (this is what > > happened > > when switching number types or the multiselect metaproperty > of a list > > property). > > > > If we remove it, then we'll completely remove a lot of data. > And is a > > warning enough for that? Probably we need a mass rollback > utility that > > is able to revert bulk changes. > > > > My take is that we should remove the data, but what do > others think?