Re: tearing my hair, ok here is a compilable example.

[Stephen J. Butler]

It has something to do with Class1 being a subclass of
NSObjectController. This code works for me with the same IB
connections (sorry, had to reformat; it's my compulsion):

#import <Cocoa/Cocoa.h>

@interface Class1 : NSObject
{
    BOOL canLink;
}

- (BOOL) canLink;

- (IBAction) change:(id)v;

@end


#import "Class1.h"

@implementation Class1

- (BOOL) canLink
{
    NSLog( @"%s %d nc:%p", _cmd, canLink, self );
    return canLink;
}


- (IBAction) change:(id)v
{
    [self willChangeValueForKey:@"canLink"];
    canLink = !canLink;
    [self didChangeValueForKey:@"canLink"];

    NSLog( @"%s %d", _cmd, canLink );
}

- (void) setCanLink:(BOOL)aValue
{
    canLink = aValue;
}

@end


#import <Cocoa/Cocoa.h>

@class Class1;

@interface Class2 : NSObject
{
    IBOutlet Class1 *class1;
}

- (BOOL) myMethod;

@end


#import "Class2.h"
#import "Class1.h"

@implementation Class2

+ (NSSet*) keyPathsForValuesAffectingMyMethod
{
    NSLog( @"%s", _cmd );
    return [NSSet setWithObject:@"class1.canLink"];
}

#pragma mark -

- (void) awakeFromNib
{
    NSLog( @"%s class1:%p", _cmd, class1 );

    [self addObserver:self
           forKeyPath:@"myMethod"
              options:NSKeyValueObservingOptionNew
              context:[Class2 class]];
}

- (void) observeValueForKeyPath:(NSString*)keyPath
                       ofObject:(id)object
                         change:(NSDictionary*)change
                        context:(void *)context
{
    NSLog( @"%s %@", _cmd, keyPath );
    if (context == [Class2 class])
    {
        if ([keyPath isEqualToString:@"myMethod"])
        {
            NSLog( @"newvalue - myMethod:%d", [self myMethod] );
        }
    }
    else
    {
        [super observeValueForKeyPath:keyPath ofObject:object
change:change context:context];
    }
}

- (BOOL) myMethod
{
    return [class1 canLink];
}

@end



On Thu, Oct 16, 2008 at 1:18 AM, Chris Idou <[EMAIL PROTECTED]> wrote:
> That thought had occured to me, but making it readwrite doesn't seem to help. 
> Cocoa NIB loading doesn't seem to call accessors, it seems to access them 
> more directly. I even tried this:
>
>
> -(Class1 *)class1 {
>        return class1;
> }
>
> -(void)setClass1:(Class1 *)v {
>        NSLog(@"setClass1: %@", v);
>        [self willChangeValueForKey:@"class1"];
>        class1 = v;
>        [self didChangeValueForKey:@"class1"];
> }
>
> But they don't get called.
>
> I even tried adding to awakeFromNIB:
>
>        id old = [self class1];
>        [self setClass1:nil];
>        [self setClass1:old];
>
> To try and force the issue, but to no avail.
>
> Someone has observed that my code works when called from main() and bypassing 
> IB. But it still doesn't work when loaded from a NIB!
>
>
> --- On Wed, 10/15/08, Quincey Morris <[EMAIL PROTECTED]> wrote:
>
>> From: Quincey Morris <[EMAIL PROTECTED]>
>> Subject: Re: tearing my hair, ok here is a compilable example.
>> To: cocoa-dev@lists.apple.com
>> Date: Wednesday, October 15, 2008, 10:54 PM
>> On Oct 15, 2008, at 22:13, Chris Idou wrote:
>>
>> > @class Class1;
>> > @interface Class2 : NSObject {
>> >    IBOutlet Class1 *class1;
>> >
>> >
>> > }
>> > @property(readonly) Class1 *class1;
>> > -(BOOL)myMethod;
>> > @end
>> >
>> > #import "Class2.h"
>> > #import "Class1.h"
>> >
>> > @implementation Class2
>> >
>> > @synthesize class1;
>> >
>> > ...
>> >
>> > - (void)awakeFromNib {
>> >    [self addObserver:self
>> >           forKeyPath:@"myMethod"
>> >              options:NSKeyValueObservingOptionNew
>> >              context: [Class2 class]];
>> >
>> > }
>> >
>> >
>> > + (NSSet *)keyPathsForValuesAffectingMyMethod {
>> >
>> NSLog(@"keyPathsForValuesAffectingMyMethod");
>> >    return [NSSet
>> setWithObject:@"class1.canLink"];
>> > }
>>
>> I think your problem is that Class2 isn't properly KVO
>> compliant for
>> the key "class1". Consider what happens when your
>> nib is loaded. At
>> some point, the nib loader needs to set "class1"
>> to its correct value.
>> Since the property is readonly and synthesized, there's
>> no setter
>> method, so the instance variable is changed directly.
>> (I'm going from
>> memory here, but I believe that's what documented to
>> happen.) That
>> presumably fails to trigger any KVO notifications, and your
>>
>> "keyPathsForValuesAffectingMyMethod" is not
>> consulted.
>>
>> Try this:
>>
>> > ...
>>
>> > @interface Class2 ()
>>
>> > @property(readwrite) Class1 *class1;
>> > @end
>>
>> >
>>
>> > @implementation Class2
>> >
>> > @synthesize class1;
>> > ....
>>
>> If my theory is correct, that should cause the outlet to be
>> set via a
>> KVC-compliant setter, and the keypath dependency should
>> start working.
>>
>>
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>
>
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