Re: Source list tree nodes able to represent different entities

FROM : Sebastian Morsch
DATE : Mon Dec 31 07:10:15 2007

Thank you for the quick answer mmalc!

You're right, a "TreeNode" entity is probably not useful for concrete 
objects that only represent other data entities. I will rather try 
using it as an abstract superclass for my data entities to let them 
inherit the attributes NSTreeController expects.

NSTreeController will then be assigned to the "TreeNode" entity rather 
than its subclasses (the data entities) for the sake of flexibility.

I only will have to insert new objects directly into the managed 
object context myself and not with NSTreeController's newObject method 
because it would only create TreeNode-objects.


I hope I got it right now, thanks again!




Am 31.12.2007 um 02:34 schrieb mmalc crawford:

>
> On Dec 30, 2007, at 4:51 PM, Sebastian Morsch wrote:
>

>> But I don't know how to work around the fact that a relationship 
>> like my TreeNodes "representedObject" wants a single entity it 
>> relates to. I want it to relate to more than one entity!
>>

> First, do you need to use a TreeNotes entity?  Can you not just use 
> the data entities directly.
>
> Note:
> "An NSTreeController requires that you describe how the tree of 
> objects is traversed by specifying the key path for child objects. 
> All child objects for the tree must be key-value-coding compliant 
> for the same child key path. If necessary you should implement 
> accessor methods in your model classes, or categories on those 
> classes, that map the child key to the appropriate class-specific 
> method name."
>
> <http://developer.apple.com/documentation/Cocoa/Reference/ApplicationKit/Classes/NSTreeController_Class/Reference/Reference.html

> >
>
>

>> Unfortunately, the usual example-suspects (CoreRecipies, SourceList 
>> Sample) seem to work with only one entity/class.
>> So does anyone know how to implement a source list tree that points 
>> to objects of different entities? Any help is greatly appreciated!! 
>> Thanks.
>>

> Use entity inheritance.  Define an entity (perhaps abstract) that 
> defines the relationship, then implement the other entities as sub-
> entities.
>
> mmalc