Re: Tree rest resource and sorting

Best doc is the one from Apple:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreData/Articles/cdFAQ.html#//apple_ref/doc/uid/TP40001802-CJBDBHCB

See 'How do I fetch objects in the same order I created them?' about collections and core data.

I'm using core data 90% via RestKit: https://github.com/twotoasters/RestKit

If you want checkout the example 'RKTwitterCoreData' to see how it works (branch 67-object-mapping-2.0).
I can also send a mockup how I mapped gallery3 json responses (tree & item).

-------- Original-Nachricht --------
> Datum: Sun, 5 Jun 2011 16:44:49 -0700
> Von: Bharat Mediratta <[email protected]>
> An: David Steinberger <[email protected]>
> CC: [email protected]
> Betreff: Re: [Gallery-devel] Tree rest resource and sorting

> On Sun, Jun 5, 2011 at 3:44 PM, David Steinberger
> <[email protected]>wrote:
> 
> >
> > Right after I sent the message I realized that I'd be beaten up by that.
> >
> > So let me give details: Core Data doesn't store NSArray, but NSSet:
> >
> >
> http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSSet_Class/Reference/Reference.html
> >
> > Yes it's platform specific. but right now iOS is the most common one.
> > Core Data is the best way to serialize objects (IMHO) and I really want
> to
> > use it.
> >
> 
> Ok.  I'm reading through the Core Data docs, but I'm new to it and there
> are
> a ton of docs out there.  Can you point me at relevant docs that talk
> about
> how Core Data does its underlying storage?
> 
> I assume that at some point you're going to coerce the NSSet into an
> NSArray
> by applying a sort order over the given field.  But it's a little
> surprising
> that the initial ordering isn't preserved somewhere...
> 
> 
> >
> > Why should it be wrong to indicate the sort by an attribute?
> > It doesn't impact the server-side at all.
> >
> 
> But it doesn't belong on the server side, either.  We're already sending
> an
> ordered list -- adding an ordering field is redundant.  This is really a
> limitation on the client side and it should be fixed there.  Yes, I'm
> being
> a bit of a purist but I hate crapping up our APIs to handle edge cases. 
> If
> this is the only way to do it, I'll be grumpy but I'll fiddle with the
> server side code.  But I'd like to be convinced that there  isn't some way
> to do it in Core Data.  Surely this must be a common use case.
> 
> 
> >
> >
> > On 6/6/11 12:16 AM, Bharat Mediratta wrote:
> >
> >
> >  Hm.  An array is an ordered list, and I would expect NSArray to
> maintain
> > the ordering --
> >
> http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/NSArray.html seems
> > to bear that out.  Are you seeing it lose the ordering?
> >
> >  Even if it was, I'd expect that this is a platform specific problem so
> > I'd expect it'd be something you'd fix on your side by updating the
> entity
> > after you load it.  Doing it on the server side smells wrong to me.
> >
> >  Thoughts?
> >
> > On Wed, Jun 1, 2011 at 10:55 AM, David Steinberger
> <[email protected]>wrote:
> >
> >>  Team,
> >>
> >> I'm reworking the data model of my iPhone app.
> >> One thing I want to revisit is how I deal with the tree rest resource
> >> (tree_rest.php).
> >>
> >> Reason:
> >> I know that the tree_rest.php delivers the objects in the right order,
> but
> >> this doesn't help me much.
> >> I need to store and retrieve the array and by doing such an operation
> with
> >> an array the order might be lost.
> >>
> >> Proposed solution:
> >> The patch attached adds a relative_position attribute to each entity.
> Via
> >> this attribute the entity order can be reconstructed at any time.
> There's no
> >> impact on performance and overall structure.
> >>
> >> Please review and merge to master or propose something even better.
> >>
> >> Thanks,
> >>   David
> >>
> >> ---
> >>
> >> FYI Details:
> >> I use core data to cache all objects (tree/album, items, tags, ...).
> Core
> >> data is kind of a database for objects on iOS. The tree is modeled via
> a
> >> Class that has a NSString property that holds the url (that's the
> primary
> >> key) and a NSArray that holds all the entities.
> >> But when I retrieve the object-graph iOS applies any sorting. ==> A
> >> sort-attribute is needed.
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
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> >>
> >
> >

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