Re: Tree Data Structure in objc-C?
Re: Tree Data Structure in objc-C?
- Subject: Re: Tree Data Structure in objc-C?
- From: Chris Hanson <email@hidden>
- Date: Sun, 27 Nov 2005 22:53:03 -0800
On Nov 27, 2005, at 7:57 PM, David Chan wrote:
I was wondering what is the best approach to the following scenario:
I have a library application where I intend to store my books under
some
categories. Now I have a NSOutlineView to do that interface wise.
But how
should I store the categories? The problem is that user should be
allowed to
create as many categories and subcategories as they want, much like
the
behavior of folders tree. Also I need to associate each book with a
category, and users should have freedom to change the book's
category, just
like the case of moving the file from one folder to another.
Core Data makes designs like this very straightforward. You just
define your entities and the relationships between them, and then
work with object graphs consisting of instances of those entities.
If you don't use Core Data, you'll need to consider carefully how
object ownership works across your documents' object graphs in order
to avoid retain cycles. The simple trick to avoiding that is to not
have ownership between model objects in the object graph; your
documents own their model objects and retain them (via "master"
arrays or sets) while the model objects just relate to each other and
don't retain.
-- Chris
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