Re: Keyed archiver

FROM : Gerriet M. Denkmann
DATE : Sun Nov 21 13:53:09 2004

On 21.11.2004, at 13:00, Jonathan Jackel wrote:

>
> On Nov 21, 2004, at 4:47 AM, Gerriet M. Denkmann wrote:
>

>> I have an object, which I want to archive.
>>
>> - (void)encodeWithCoder:(NSCoder *)coder
>> {
>>     [ coder encodeObject: myString  forKey: @"myString" ];
>> }
>>
>> - (id)initWithCoder:(NSCoder *)decoder
>> {
>>     myString = [ decoder decodeObjectForKey: @"myString" ];
>>     NSLog("@ myString: \"%@\");
>>     return self ;
>> }
>>
>> When myString is @"$noll" everything works just fine.
>> But if myString is @"$null" (note the changed vowel) the unarchive
>> string is nil.

>
> Four things:
>
> 1. Always call super in your init method.  Always.

Yes, you are right. Now my initWithCoder: starts with:
  self = [ super init ];
  if ( self == nil ) return nil ;

>
> 2. Your NSLog statement looks wrong.  There's no parameter and no
> closing quote mark (the escape sequence at the end doesn't count). 
> And the first @ should go outside the first quote mark.

Right again; as you sure have already realized, this statement has
never been compiled - it was just typed in Mail. And I have to
apologize for the sloppy typing.
It should have been:
NSLog(@"myString = %@", myString);

>
> 3. Use accessors to set ivars.  Otherwise your ivars will be
> deallocated prematurely.  This could be your problem.

Well, as I log the value immediately after decodeObjectForKey: there is
not much chance for premature deallocation.

>
> 4. I think it is a good practice to use constant strings, defined
> outside the implementation, as keys.  That way you will get a compiler
> warning if you type them incorrectly.  For example:

I agree that this is a good practice; but alas, it has nothing to do
with my problem.

>
> Try it that way and see if you still have problems.

I did and I still have.
I can archive and restore a string with the value "$noll" but I cannot
do the same with "$null".


Kind regards

Gerriet.