On Dec 8, 2008, at 04:18, Steven Hamilton wrote:
I have a custom NSWindowController called budgetController.
Interface thus (cropped a bit)
@interface MLBudgetController : NSWindowController {
IBOutlet NSArrayController *incomeEnvelopeController;
NSManagedObject *selectedIncomeEnvelope;
}
My window has an NSPopupButton bound to my NSArraycontroller
*incomeEnvelopeController. The selectedObject binding is bound to
the selectedIncomeEnvelope above. The controller sources Core Data
for my "Envelope" entities and on running, it fetches and displays
the set of entities fine showing the correct values. It also sets
the selectedIncomeEnvelope fine too.
But on first load I have a "No Value" in the popup. Selecting an
entry removes the No Value from the list. In my budgetController's
windowDidLoad{} function I'm attempting to set the
selectedIncomeEnvelope to the first object in the array like so;
selectedIncomeEnvelope= [[incomeEnvelopeController arrangedObjects]
objectAtIndex:0];
However, the arrangedObjects array, while existing, contains zero
objects. I've checked the Outlet is connected ok. A timing issue of
some sort?
No. Based on the above, your code isn't KVO compliant.
First of all, it's important to realize that nothing is ever bound to
an instance variable (selectedIncomeEnvelope), but to an object
property (MLBudgetController instance, key "selectedIncomeEnvelope").
The two are not the same thing, although KVO will *pretend* there's a
property when there's only a variable (which appears to be your case,
and which is why it works some of the time).
When you go to set the initial selected object, you need to change the
property, not the variable. This is easiest if you actually define the
property (or write the getter & setter):
@property NSManagedObject *selectedIncomeEnvelope;
...
@synthesize selectedIncomeEnvelope;
...
self.selectedIncomeEnvelope= [[incomeEnvelopeController
arrangedObjects] objectAtIndex:0];
That should cause the proper KVO notification to be sent, and for the
correct object to be selected in the user interface.
Or, if you don't want to define the property explicitly, then you have
to generate the notification yourself:
[self willChangeValueForKey: @"selectedIncomeEnvelope"];
selectedIncomeEnvelope= [[incomeEnvelopeController arrangedObjects]
objectAtIndex:0];
[self didChangeValueForKey: @"selectedIncomeEnvelope"];
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