On Jan 28, 2012, at 13:28 , Mikael Wämundson wrote:
> I have put an NSMutableArray (dataObjectArray) in my class
> DataObjectCollection. I have also made it possible to add objects to
> DataObjectCollection and hence the array by implementing
> - (void)addDataObject:(DataObject *)theDataObject
> {
> NSIndexSet *loneIndex = [NSIndexSet indexSetWithIndex:[[self
> dataObjectArray] count]];
> [self willChange:NSKeyValueChangeInsertion valuesAtIndexes:loneIndex
> forKey:@"dataObjectArray"];
> [dataObjectArray addObject:theDataObject];
> [self didChange:NSKeyValueChangeInsertion valuesAtIndexes:loneIndex
> forKey:@"dataObjectArray"];
> }
>
> In InterfaceBuilder I have put an ArrayController with ContentArray bound to
> "myAppDelegate".theDataObjectCollection.dataObjectArray
> I have created bindings between the ArrayController and the columns of an
> NSTableView is
>
> Problem:
> Programmatically adding objects to my DataObjectCollection is not observed by
> the ArrayController.
>
> I earlier had the dataObjectArray directly in my AppDelegate and then the key
> value observing worked.
>
> Is there something I need to do with my class DataObjectCollection to make
> the observing work, i.e. to make it KVO compliant?
Well, you're doing this the wrong way. Here are the steps, starting over from
the beginning:
1. Add a NSMutableArray* 'dataObjectArray' instance variable to your
DataObjectCollection class. This is part of the private implementation, and
shouldn't be visible to the clients of the class. To make sure of this,
override '+accessesInstanceVariables' in DataObjectCollection to return NO.
2. Decide on a client-visible (public) property name for your indexed
collection property. Use a plural noun, such as "dataObjects". Choosing a name
different from the instance variable name emphasizes the difference between the
property (public API) and the variable (private backing store).
3. Define a *readonly* "dataObjects" @property for DataObjectCollection, with
type 'NSArray*' (NOT 'NSMutableArray*'), and implement the getter to return
'dataObjectArray'.
4. Implement the basic indexed accessor methods:
-insertObject:inDataObjectsAtIndex:
-removeObjectFromDataObjectsAtIndex:
5a. If you want a convenience method like 'addDataObject:', implement it like
this:
- (void) addDataObject: (DataObject*) dataObject {
[self insertObject: dataObject inDataObjectsAtIndex:
self.dataObjects.count];
}
5b. I happen to prefer not to create such convenience methods (because you
often end up creating lots of them to parallel the NSArray methods). I usually
create an auxiliary method:
@property (readonly) NSMutableArray* mutableDataObject;
implemented like this:
- (NSMutableArray*) mutableDataObjects {
return [self mutableArrayValueForKey: @"dataObjects"];
}
so you can add an object like this:
[dataObjectCollection.mutableDataObjects addObject];
6. Bind your array controller's content to
myAppDelegate.theDataObjectCollection.dataObjects.
If you follow these steps, your array property is 100% KVO compliance, *and* it
cannot be tampered with non-KVO-compliantly from outside, either
programmatically or via KVC.
(All code typed in Mail, so apologies for any typos and omissions.)
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