On Apr 28, 2010, at 04:28, Graham Cox wrote:
> Well, there is - (void)encodePoint:(NSPoint)point forKey:(NSString *)key, but
> you can only use that from within a call to -encodeWithCoder:. If you have a
> need to archive something from "outside", as in the OP's code, wrapping it in
> a NSValue doesn't work (really, that seems to be an oversight on NSValue's
> compliance with NSCoding), but converting it to a string will work. Same for
> Rects, sizes et. al. I would think it's odds-on that the internals of
> -encodePoint:forKey: just make a call to NSStringFromPoint anyhow.
I would really hope that the last statement *isn't* true. :) If my point's X
and Y are not integral, using a string would in general not preserve the
floating point values precisely.
As to the inability to archive NSValue-encoded structs, note that it's the
archiver that's complaining, not the NSValue object. Keyed archivers don't
support structs:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/Archiving/Tasks/codingctypes.html
So why would NSValue tell an archiver to encode its contents as a struct?
Because the thing *is* a struct and that's all NSValue knows about it.
Instead of trying to solve this problem with strings, I use immutable,
objectified versions of these structs, like this:
> @implementation MyPoint
>
> @synthesize point;
>
> - (id)initWithPoint:(NSPoint)initialPoint {
> self = [super init];
> if (!self)
> return nil;
> point = initialPoint;
> return self;
> }
>
> - (id) initWithCoder: (NSCoder*) coder {
> self = [super init];
> if (!self)
> return nil;
> point = [coder decodePointForKey: @"point"];
> return self;
> }
>
> - (void) encodeWithCoder: (NSCoder*) coder {
> [coder encodePoint: point forKey: @"point"];
> }
>
> - (NSUInteger)hash {
> return point.x * point.y;
> }
>
> - (BOOL)isEqual:(id)object {
> if (!object)
> return NO;
> if (![object isKindOfClass:[self class]])
> return NO;
> MyPoint* otherPoint = object;
> return NSEqualPoints (self.point, otherPoint.point);
> }
(I never bothered to go back and write a decent hash function.)
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