Re: -observeValueForKeyPath:ofObject:change:context: only defined for abstract class. Runtime error
Re: -observeValueForKeyPath:ofObject:change:context: only defined for abstract class. Runtime error
- Subject: Re: -observeValueForKeyPath:ofObject:change:context: only defined for abstract class. Runtime error
- From: Jonathon Mah <email@hidden>
- Date: Tue, 11 Oct 2005 22:32:02 +0930
Carlos,
On 2005-10-11, at 21:18, Carlos Rivera wrote:
I have two entities specified in XCode{Trip, Car}. Trip has a 1 to 1
relationship with Car, while Car has 1 to many to Trip. Now Car has
a property(totalDistance) which is dependent on the sum of all the
properties in each
Trip(distance).
<snip>
So everything compiles just fine but when I run and I change the
distance in Trip I get the following error:
-observeValueForKeyPath:ofObject:change:context: only defined for
abstract class. Define -[NSManagedObject
observeValueForKeyPath:ofObject:change:context:]!
It sounds like the argument passed to setCar: is not an instance of
your Car class.
Also, I don't remember the details, but I think Core Data has a built
in mechanism for calculating aggregates of data (sum, average, max,
min, etc.). In which case you don't need to handle it yourself.
Jonathon Mah
email@hidden
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