gistfile1.txt

@implementation Shape : CPObject
{
CGRect mRect;
CPColor mColor;
}

- (void)encodeWithCoder:(CPCoder)aCoder
{
[aCoder encodeRect:mRect forKey:"rect"];
[aCoder encodeObject:mColor forKey:"color"];
}

- (id)initWithCoder:(CPCoder)aCoder
{
self = [super init];
if (self)
{
mRect = [aCoder decodeRectForKey:"rect"];
mColor = [aCoder decodeObjectForKey:"color"];
}
return self;
}

@end

// Later on

data = [CPKeyedArchiver archivedDataWithRootObject:shapesArray]

// to decode

shapesArray = [CPKeyedUnarchiver data]