On Mar 16, 2009, at 11:20 AM, Stuart Malin wrote:
How does one know just which methods are "required primitive"
methods for some class? Is that discernible from documentation?
Header file?
They are documented, but the header files also split the primitives
from the rest.
Look at NSString:
@interface NSString : NSObject <NSCopying, NSMutableCopying, NSCoding>
/* NSString primitive (funnel) methods. A minimal subclass of NSString
just needs to implement these, although we also recommend
getCharacters:range:. See below for the other methods.
- (NSUInteger)length;
- (unichar)characterAtIndex:(NSUInteger)index;
@end
@interface NSString (NSStringExtensionMethods)
- (void)getCharacters:(unichar *)buffer;
- (void)getCharacters:(unichar *)buffer range:(NSRange)aRange;
...
@end
Then, NSMutableString:
@interface NSMutableString : NSString
/* NSMutableString primitive (funnel) method. See below for the other
mutation methods.
*/
- (void)replaceCharactersInRange:(NSRange)range withString:(NSString
*)aString;
@end
@interface NSMutableString (NSMutableStringExtensionMethods)
- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;
- (void)deleteCharactersInRange:(NSRange)range;
...
@end
The primitive or "funnel" methods are all you need to implement.
NSString and NSMutableString implement all of the other methods
entirely in terms of the primitive methods, directly or indirectly
(i.e. some other method may be implemented in terms of another method
implemented using only the funnel methods).
You only *need* to implement the funnel methods.
You might, however, find that you need to implement some of the others
for efficiency's sake (as implied by the comment in NSString). And
that is exactly what concrete subclasses do -- they implement highly
optimized versions of the other methods specifically for performance
reasons.
Same pattern holds true for the other class cluster classes.
b.bum
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