Re: encoding objects containing NSData ivars using NSKeyedArchiver

[Jens Alfke]

On 12 Mar '08, at 7:44 AM, Daniel Thorpe wrote:

I'm trying to archive an object using NSKeyedArchiver. The object is question has quite a complex structure, and one of it's instance variables is an NSMutableData. I've tried using

[coder encodeObject:result forKey:@"TchebichefMoment_momentData"];
which doesn't seem to do anything at all

Really? That should work fine. I've encoded NSData objects like this many times, so I'm pretty sure there's not a bug in NSKeyedArchiver. Have you set a breakpoint and verified that 'result' is non-nil when this is called?

        const double *dataPtr = (const double *)[result bytes];

[coder encodeBytes:dataPtr length:(NSUInteger)(N*N*sizeof(double)) forKey:@"TchebichefMoment_momentData"];

...

                NSUInteger len;

                self.result = [[NSData alloc] initWithBytes:dataPtr length:len];

const double *dataPtr = (const double *)[coder decodeBytesForKey:@"TchebichefMoment_momentData" returnedLength:&len];

—Jens

This should work too, although if the array is very large it may use more memory, because the archiver keeps its own copy of the returned data block. PS: There's no need to prefix the key strings with a namespace, e.g. "TchebichefMoment_". The keys are specific to each object. You just shouldn't use a name that's also used by a superclass.

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