Comments on: Mistakes I Made Using Bindings Without Core Data

By: jobi

jobi — Sun, 11 Jun 2006 21:36:55 +0000

The reason you have to use the workaround in 2) is that “setIsIndeteriminate:” is not the proper accessor for a value named “indeterminate”. From the KVC system’s perspective, you are modifying indeterminate without warning (unless you call will/didChange). The proper name would have been “setIndeterminate:”; i.e. the value being set is “indeterminate”, not “isIndeterminate”.

If you try to use setValue:forKey:, you’ll probably see that your setter method won’t be called (even though the variable will change, since in that case KVC just goes and muddles with your object directly).

By: BrianC

BrianC — Wed, 07 Jun 2006 16:00:39 +0000

Marcus, thanks for the comment. I actually like the getters and setters. I’m not a fan of the ‘setValue:forKey:’ stuff. I like seeing [self setIsIndeterminate:YES/NO] instead of the setValue:forKey stuff. I think the getters and setters read better and in most cases are worth their effort.

By: Marcus S. Zarra

Marcus S. Zarra — Wed, 07 Jun 2006 15:24:33 +0000

Going to have to disagree with you on number 2. I have never had to call willChange and didChange inside of a set method.

In fact, if you want some more magic instead, remove the getter and setter completely! Try this at home...

In your interface:

BOOL isIndeteriminate;

When you want to change this value:

[self setValue:[NSNumber numberWithBool:YES] forKey:@"isIndeteriminate"];

It will update the value AND notify any listeners that the value has changed. To read the value call:

[[self valueForKey:@"isIndeteriminate"] boolValue];

Note: valueForKey is what IB uses to look up this value.

There is no need (at least in Tiger, have not messed with 10.3 in a while) for simple getters and setters.

Even without using these methods, there should be no reason to use willChange and didChange in your setter. The setter handles the notification for you "automagically".

Marcus S. Zarra Zarra Studios LLC www.zarrastudios.com Simply Elegant Software for OS X

By: BrianC

BrianC — Wed, 07 Jun 2006 14:23:12 +0000

Thanks Jean-Fancois. I’ve updated the post to point out that I was just wrong on that one (which is good).

By: Jean-Francois Roy

Jean-Francois Roy — Wed, 07 Jun 2006 13:48:46 +0000

This problem is stange to me, because the KVC documentation clearly states in http://developer.apple.com/documentation/Cocoa/Conceptual/KeyValueCoding/Concepts/DataTypes.html that KVC will automatically wrap and unwrap BOOL as an NSNumber.