Re: [xwiki-devs] [VOTE] Object properties references (was [proposal][discussion])

Hi devs, to resume, and try to converge to an implementable version, I propose: 1/ adding only OBJECT and PROPERTY EntityTypes for the moment, referring to an object instance and a property instance in a document (a property ref would have an object as a parent which would have a document reference as a parent), and limiting the implementation to references to properties of object instances (leaving aside type definitions ftm). here's my +1 for this. 2/ using a serialization of the form wiki:Space.Page^className[objectnumber]#property and a) using indexed ('multivalued') references, adding an additional IndexedEntityReference class, to which API caller would have to cast. ObjectReference would be such an IndexedEntityReference and provide object related helper functions. b) className[objectnumber] is used as an 'object name', it would be the name of the object reference, and it would be the caller of the generic API that would have to parse&  serialize this kind of strings to actually extract classname and object index. However, this would again be all hidden behind the ObjectReference API. I'm 0.5 and 0.5 between the two, any would suit my purpose. An additional question is what would wiki:Space.Page^className (and wiki:Space.Page^className#property) mean: i) nothing, we consider it as invalid reference, we'll fix that later, we keep it simple ftm my +1 goes for this ii) all objects of class className in the document iii) first object of that class in the document (as XWikiDocument#getObject(className) does) iv) a shortcut for wiki:Space.Page^className[0] (which, note, does not necessarily mean the first object in that document, since indexing of objs in a document is not recomputed when objects are deleted). WDYT? Thanks, Anca On 01/13/2010 02:42 PM, Anca Luca wrote: > Hi devs, > > Short story: > 1/ add the CLASS, OBJECT, PROPERTY EntityTypes in the model > > +1 > > 2/ serialization for referencing a property of an object >       a) wiki:Space.Page^className[objectNumber]#property >       b) wiki:Space.Page^className#objectNumber$property > +0.75 for b) > > Long story: > > 1/ I would need to extend the EntityReference to be able to target a > property in an object in a document. > For this, I will need to add > >       /** >        * Represents a Class Entity >        */ >       CLASS, > >       /** >        * Represents an Object Entity. >        */ >       OBJECT, > >       /** >        * Represents a Property Entity >        */ >       PROPERTY, > > in the EntityType. Although I would prefer an extensible framework that > would allow to extend the possible entity types without changing an enum > in the platform (for any API user to be able to define its own > references), I think this is fairly extensible (these are key concepts > in the xwiki model and I don't think they would be changed that soon, > and their interpretation is flexible, they could be combined with any > parent to generate either references to class definitions or instances). > here's my +1 for this. > > 2/ I would also need a 'standard' string serialization for these. Now, > there's also the option to do it in my own module (annotations) because > only I need it ftm, but I prefer to have a platform wide approach. Opinions? > There are 2 choices, with a potentially different combination of separators: > > a/ wiki:Space.Page^className[objectNumber]#property > > pros: it's a suggestive way to access objects by number ([] is the > standard syntax for array indexed access and the objects are accessed by > index), [] is supported by JCR so maybe we should support it too > cons: [] is somewhat inconsistent with all other separators which are > just one separator, to the left (right) of the entity, harder to > implement the [] separators on the current framework > > b/ wiki:Space.Page^className#objectNumber$property > > pros: inline with the separator usage we already have (and easier to > implement for this reason), could be easier refactored to contain an > object name instead of the number > cons: $ separator can collide with velocity syntax (can potentially > cause trouble when used in velocity -- an alternative could be the pipe > |), could be harder to drop the object number part of the reference to > refer a property in a class (if wanted, in the future) > > I have no other argument between a) and b) but the implementation speed > one, so I'd go for a b)-like approach, in the spirit of the current > separators. > > WDYT? > > Thanks, > Anca