Core Data natively supports attributes that are of type NSString, NSNumber, or NSData. You can however use other types with a bit of extra work. If you have an attribute that is a scalar value such as BOOL, you can have your managed object persist it by first converting it to a NSNumber. For example, CheckBox is a NSManagedObject with an attribute called checked that is of type BOOL. BOOL in Objective-C can easily be converted to and from a NSNumber.
The header file contains the BOOL attribute for CheckBox.
// CheckBox.h
#import
@interface CheckBox : NSManagedObject {
}
@property(nonatomic) BOOL checked;
@end
The implementation file contains a PrimitiveAccessors category for the underlying primitiveChecked value, which stores the checked value as a NSNumber. We then override the accessors and mutators for the checked attribute to convert the BOOL value to and from a NSNumber.
// CheckBox.m
#import "CheckBox.h"
@interface CheckBox (PrimitiveAccessors)
@property (nonatomic, retain) NSNumber *primitiveChecked;
@end
@implementation CheckBox
- (BOOL)checked {
[self willAccessValueForKey:@"checked"];
BOOL isChecked = [[self primitiveChecked] boolValue];
[self didAccessValueForKey:@"checked"];
return isChecked;
}
- (void)setChecked:(BOOL)isChecked {
[self willChangeValueForKey:@"checked"];
[self setPrimitiveChecked:[NSNumber numberWithBool:isChecked]];
[self didChangeValueForKey:@"checked"];
}
@end
