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Re: core data app questions - help!
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Re: core data app questions - help!


  • Subject: Re: core data app questions - help!
  • From: mmalc crawford <email@hidden>
  • Date: Sat, 1 Sep 2007 15:41:03 -0700


On Sep 1, 2007, at 9:57 AM, Ricardo Strausz wrote:
But the main thing to have in mind is that if you have a good model, you can fetch (see) your data in many ways, just by free.

This us at best misleading; fetches in general are *not* free -- a fetch causes Core Data to go back to the persistent store, which is an expensive operation.
You can certainly fetch your data in many ways, but constructing the correct fetch request is itself not always conceptually free (i.e. you have to think about it).


Also, you may have to adjust your interface to.

Well, yes...


As I understand, your model is something like W<<-->S : W<<-->I (with the obvious meanings).
The easiest part is to put at work your to-many relations: any of the tutorials that come with the tools will explain (in particular, see http://developer.apple.com/cocoa/coredatatutorial/index.html )


This explains how to create a "default" interface using bindings. Like Core Data, bindings are not a beginner technology.

If you're able to create your application solely using drag-and-drop/ point-and-click technologies, then fine. But typically there's more to it than that and if you don't understand the fundamentals on which those technologies are based then you're left several levels of abstraction up in the air with no idea how to progress...

For number one, I would recommend to add an entity with dates, and with relations W<<-->D, so by clicking in a date you can see only those objects in W with that date... if this can be done with a nicer interface (a calendar) will be your research – please let us know ;^)

It's not clear exactly what this means or how it helps.


For the last, you will have to implement a notification centre that advise you whenever the table changes, so you can calculate the needed sum using something like [[table displayedObjects] @sum(duration)].

Again this is at best misleading -- the precise mechanism used to propagate change notifications will depend on the application architecture implemented. Moreover, there is no 'displayedObjects' method, and you cannot send a @sum(duration) message. *If* you're using bindings, then you might *bind* the 'value' of a text field to the sum of duration properties of the *arrangedObjects* in a relevant array controller.

mmalc_______________________________________________

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