First off, thanks very much for the lengthy response. My initial
response to your post was rejected for length, so I am trying to
abbreviate here, pinpointing areas of confusion.
Hmm. An NSArrayController doesn't manage tables, it manages an
array (as its name implies). So, do you have an array somewhere
with instances of the Word class? Where is it? For example, is it
a property of File's Owner, with a key "words"?
The class structures are:
Word has three ivars {characters, reading, english} (all strings)
WordList has (for now) just one ivar {wordList} (a mutable array)
Word has the appropriate accessors to conform to KVC. That's as far as
my certainty goes. Here are the main points of confusion.
1. I'm not sure about WordList. I got an error message about wordList
not being KVC compliant. So after reading your response and additional
links on KVC compliance for arrays (one-to-many relations, think it
was), I suspected I might need to provide WordList with something
like....
- (void)insertObject:(Word *)word inWordListAtIndex:(unsigned
int)index {
[[self wordList] insertObjectAtIndex: index];
}
- (void)removeObjectFromWordListAtIndex:(unsigned int)index {
[[self wordList] removeObjectAtIndex: index];
}
Unfortunately, that didn't work.
2008-06-05 14:06:20.015 Table Practice[670:10b] An uncaught exception
was raised
2008-06-05 14:06:20.016 Table Practice[670:10b] [<AppController
0x13aca0> valueForUndefinedKey:]: this class is not key value coding-
compliant for the key wordList.
2008-06-05 14:06:20.016 Table Practice[670:10b] *** Terminating app
due to uncaught exception 'NSUnknownKeyException', reason:
'[<AppController 0x13aca0> valueForUndefinedKey:]: this class is not
key value coding-compliant for the key wordList.'
I recognize here that this error was generated in reference to
AppController, not WordList, but it seems crazy to me that I would
have to place KVC-compliant code in a controller. So I think something
is wrong with the bigger setup. Which brings up issue #2.
2. In my case, File's Owner is simply the proxy for NSApp, and since I
can't subclass it, it's not the place for me to add wordList, as you
suggested I might. I think you had a Doc-App structure in mind for
placing wordList in there, but I haven't really gone into Doc-Apps
yet. I'm familiar with using FO as a way to connect window controllers
to the nib. But given that I'm using NSApp as File's Owner, one
question becomes where or how to tie in my WordList instance and its
ivar worList.
This is confusing for two reasons:
a) Someone in the series of File'sOwner posts pointed out that much of
the beginner's code drops a part of the model into the nib, but that
this is bad coding practice.
b) Some bindings examples use an additional homemade controller and
some don't. I'm not quite following the reasoning behind this decision.
3. I think one thing is starting to be clear. If you are going to
truly separate M from V, then you generally make two sets of bindings.
1. Bind some view object to some controller (presumably the
NSController subclass, though I'm not totally sure).
2. Bind some controller (again, presumably the NSController subclass)
to some model object.
Maybe this leads to a key concept I'm trying to grapple. When are you
binding to values, and when to content? You suggested I look at the
reference for NSArrayController with respect to contentArray. They had
this to say:
contentArray
an indexed collection that specifies the content of the
NSArrayController.
The indexed collection is an NSArray instance or subclass, a property
that is accessible using the key-value-coding indexed accessor
methods, or is accessible through mutableArrayValueForKey:.
But I'm still a little fuzzy here. In my example, wordList is the
indexed collection. So I thought that should be it. But you said the
object class should be Word because wordList is an array of *Word*
objects. I'm obviously missing this key distinction (between value and
content), because to me either of the following sentences make sense:
a) I want my array controller to reflect (bind to) the values in the
table
b) I want my array controller to reflect (bind to) the contents of the
table
(all with the understanding that "reflecting" is a loose term to mean
a reciprocal and bidirectional communication so that changes on one
side are reflected in the other)
Now, as to the question of what to bind to (arrangedObjects,
arrangedObjects.key, selection.key, etc.), that depends on what
you're trying to accomplish. If you want to access all of the
objects in the array being managed by an array controller, you bind
to that controller's "arrangedObjects" controller key.
In my case, I think the answer is yes. I want to display everything in
the wordList => use arrangedObjects (?).
If you want to access a particular property of the objects in that
array, you specify a model key path to that property.
In my case, the answer is again yes. I want to access specific values
of those objects => use the model key path. This will be especially
true once I'm ready to add the detail view. Again, this is a point
where it seems fuzzy. To me, since my model objects are WordList and
Word, my path should be for column 1 should be wordList.word.<ivar1>.
But InterfaceBuilder is offering "self" as a starting point. I'm not
even sure who "self" is. The NSArrayController or my separate
controller containing an instance of WordList?
Typically, custom controllers are different kinds of things from
NSController-derived objects. Search the Cocoa Fundamentals Guide
for the phrases "mediating controller" and "coordinating controller".
Having at least tried bindings, that distinction is beginning to make
more sense now than it did two months ago.
4. My NSArrayController has a "content" outlet that clearly needs to
be set. What do I set it to? I could drag it to AppController (which
has the WordList instance as an ivar). Or I could drag it directly to
the table in the window. To my mind, either could legitimately be
deemed "desired content".
As the File's Owner discussion took some 70 emails to resolve itself,
I'm trying my best to pinpoint what key concepts and which parts of
the documentation and the IB interface are not making sense to me.
Maybe that will help hone in on where I've gone astray. Thanks.
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