On Aug 17, 2011, at 04:34 , Arno Oesterheld wrote:
> I am a beginner with Xcode and Objective-C and stuck with a quite simple
> thing for over two days now. I hope you can help me.
>
> My Project is deployed for OS X 10.6, it uses Garbage Collection and I am
> using Xcode 4.0.1.
>
> I made a multi document application starting with the template provided by
> Xcode. I just have one class as subclass of NSDocument.
>
> For opening documents I use initWithCoder. The decoding mithin this method
> works fine - I get the values that were saved.
> But these values are "lost" when I would like to use them in an other method
> (of the same class).
>
> I assume that I make some mistakes with using the right comibation of init: /
> initWithCoder: / initWithContentsOfURL: etc.
> The self-object does always have a different adress in the initWithCoder
> method then in the other methods.
> I tried plenty of combinations of the above methods and even tried to call
> differend methods in the super class (NSDocument) within initWithCoder.
Well, it's hard to answer your questions very clearly, because you have some
basic confusions here. You're going to have to go back and study the
documentation some more, and possibly get hold of a Cocoa tutorial boom that
leads you through some of the basics.
I think the central (but not only) point of confusion is that you seem to be
trying to archive a NSDocument object. This isn't how it works. The NSDocument
object (well, your subclass object) is a transient object, created when you
open the document and destroyed when you close it.
The *contents* of your document, also known as your data model, is what is
archived, usually to a file. It's an object or a hierarchy of objects of some
*other* class than NSDocument.
So, it makes no sense to declare your NSDocument subclass as conforming to
NSCoding.
I think what's happening now (very roughly, since you didn't show enough code
to be sure of this) is that you're archiving a NSDocument object as your data
model. When you re-open the document file, you unarchive the object, which
contains the archived data (so there is the *appearance* that it did something
right). Now you have 2 NSDocument objects -- the one that was created for you
as a result of opening the document file, and the one that was unarchived. The
second one isn't expecting to be created this way, and it kind of messes things
up.
Try reading here:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CocoaFundamentals/CocoaDesignPatterns/CocoaDesignPatterns.html#//apple_ref/doc/uid/TP40002974-CH6-SW1
especially about the MVC pattern. The NSDocument object is a *controller*. Your
archived data is a *model*.
You're also going to need to understand the information here:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Documents/Concepts/OverviewDocArchitecture.html#//apple_ref/doc/uid/20000023-BAJBBBAH
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