Don't Understand KVC Error Using Array Operators
-
I can't understand why I'm getting an exception when I try to use the
array operators.
Here's what I'm trying to do. One instance variable is a
NSMutableArray named "contacts". This array contains instances of
objects that have a "call" property, which is an NSString. I have
another instance variable, also an NSString, named "exCall". I want
to find out whether any contact has a call property that equals exCall.
(It's a ham radio logging program. Yes, I know I'm a nerd, thanks.)
The following method works:
- (BOOL)callInLog
{
if (!contacts || ![contacts count] ||
![self exCall] || ![[self exCall] length])
return NO;
NSEnumerator *e = [[self contacts] objectEnumerator];
QEContact *contact;
while (nil != (contact = [e nextObject])) {
if ([[contact call] isEqual:[self exCall]])
return YES;
} // while
return NO;
} // callsignInLog
The following method throws an exception every time:
- (BOOL)callInLog
{
if (!contacts || ![contacts count] ||
![self exCall] || ![[self exCall] length])
return NO;
return ([[self valueForKey:@"<contacts....>"]
containsObject:[self exCall]]);
} // callsignInLog
The message on the console is "Exception raised during posting of
notification. Ignored. exception: '[<QELogModel 0x15c3a0>
valueForUndefinedKey:]: this class is not key value coding-compliant
for the key <contacts....>.' invoked observer method:
'*** -[NSTextField textDidEndEditing:]' observer: 0x17a0a0
notification name: 'NSTextDidEndEditingNotification'"
Shouldn't the results of the two routines be identical? If not, why
not?
(I'm running XCode v. 3.0 on a PPC machine that's running Leopard v.
10.5.4. The target SDK is Mac OS X 10.4 (Universal), with all that
entails, such as no garbage collection or ObjC 2.0.)
Thanks for any help,
-Jon -
On Jul 8, 2008, at 8:02 AM, Jon Gordon wrote:> I can't understand why I'm getting an exception when I try to use
> the array operators.
>
> Here's what I'm trying to do. One instance variable is a
> NSMutableArray named "contacts". This array contains instances of
> objects that have a "call" property, which is an NSString. I have
> another instance variable, also an NSString, named "exCall". I want
> to find out whether any contact has a call property that equals
> exCall.
>
> (It's a ham radio logging program. Yes, I know I'm a nerd, thanks.)
>
> The following method works:
>
> - (BOOL)callInLog
> {
> if (!contacts || ![contacts count] ||
> ![self exCall] || ![[self exCall] length])
> return NO;
>
> NSEnumerator *e = [[self contacts] objectEnumerator];
> QEContact *contact;
> while (nil != (contact = [e nextObject])) {
> if ([[contact call] isEqual:[self exCall]])
> return YES;
> } // while
>
> return NO;
>
> } // callsignInLog
>
>
> The following method throws an exception every time:
>
> - (BOOL)callInLog
> {
> if (!contacts || ![contacts count] ||
> ![self exCall] || ![[self exCall] length])
> return NO;
>
> return ([[self valueForKey:@"<contacts....>"]
> containsObject:[self exCall]]);
> } // callsignInLog
>
>
> The message on the console is "Exception raised during posting of
> notification. Ignored. exception: '[<QELogModel 0x15c3a0>
> valueForUndefinedKey:]: this class is not key value coding-compliant
> for the key <contacts....>.' invoked observer
> method: '*** -[NSTextField textDidEndEditing:]' observer: 0x17a0a0
> notification name: 'NSTextDidEndEditingNotification'"
valueForKey and valueForKeyPath are two different KVC accessors.
You're using valueForKey and passing a dot-separated string. People
usually use dot-separated strings as keypaths and pass them to
valueForKeyPath.
<more info than you really need to know to fix this>
It's totally legal to pass dot-separated strings to value for key, but
the NSObject built in logic won't be able to find a property or getter
method with a sig like "<contacts....>". Mainly since
that's not a valid obj-c ivar or method name.
</more info than you really need to know to fix this>
use valueForKeyPath instead of valueForKey.>
>
> Shouldn't the results of the two routines be identical? If not, why
> not?
>
> (I'm running XCode v. 3.0 on a PPC machine that's running Leopard v.
> 10.5.4. The target SDK is Mac OS X 10.4 (Universal), with all that
> entails, such as no garbage collection or ObjC 2.0.)
>
> Thanks for any help,
>
> -Jon
--------------------------
RONZILLA -
"D'oh!"
-H. Simpson
I made the change, and it works perfectly now. Thanks very much!
On Jul 8, 2008, at 11:44 AM, Ron Lue-Sang wrote:>
> On Jul 8, 2008, at 8:02 AM, Jon Gordon wrote:
>
>> I can't understand why I'm getting an exception when I try to use
>> the array operators.
>>
>> [SNIPPAGE]
>
> valueForKey and valueForKeyPath are two different KVC accessors.
> You're using valueForKey and passing a dot-separated string. People
> usually use dot-separated strings as keypaths and pass them to
> valueForKeyPath.
>
> <more info than you really need to know to fix this>
> It's totally legal to pass dot-separated strings to value for key,
> but the NSObject built in logic won't be able to find a property or
> getter method with a sig like "<contacts....>".
> Mainly since that's not a valid obj-c ivar or method name.
> </more info than you really need to know to fix this>
>
> use valueForKeyPath instead of valueForKey.
