On Jan 13, 2010, at 7:29 PM, Richard Somers wrote:
> On Jan 13, 2010, at 7:14 AM, Jim Correia wrote:
>
>> This style is typically used for non-object BOOL values. If you use it for
>> an NSNumber attribute, you run the risk of someone familiar with the pattern
>> assuming it is a BOOL property and writing
>>
>> if ([managedObject isSelected]) {
>>
>> }
>>
>> which will of course be be true whenever the property is non-nil, no
>> regardless of the actual value.
>
> Thanks for the reply and the information. The attribute is a bool in the
> Xcode data modeler. When you copy the Obj-C 2.0 method declarations for the
> bool attribute to the clipboard this is what you get.
>
> @property (nonatomic, retain) NSNumber *selected;
>
> So I assume that Core Data frameworks default is to use a NSNumber for a bool
> value.
That is correct. Core Data always expresses its attribute as object values.
If you want to have a scalar BOOL property on your object, you can, but you
must write your own accessors. (And be aware of and deal with
-setNilValueForKey: as appropriate.)
For example:
- (BOOL)isSelected
{
NSNumber *selected = nil;
[self willAccessValueForKey: @"selected"];
selected = [self primitiveSelected];
[self didAccessValueForKey: @"selected"];
return (selected != nil) ? [selected boolValue] : NO;
}
- (void)setSelected:(BOOL)selected
{
[self willChangeValueForKey: @"selected"];
[self setPrimitiveSelected: [NSNumber numberWithBool: selected]];
[self didChangeValueForKey: @"selected"];
}
- Jim
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