Re: NSCoding protocol
Re: NSCoding protocol
- Subject: Re: NSCoding protocol
- From: Negm-Awad Amin <email@hidden>
- Date: Fri, 10 Oct 2008 18:52:41 +0200
Am Fr,10.10.2008 um 18:17 schrieb Clark Cox:
On Fri, Oct 10, 2008 at 9:09 AM, Negm-Awad Amin <email@hidden
> wrote:
Am Fr,03.10.2008 um 21:00 schrieb email@hidden:
I want MyClass to conform to the NSCoding protocol. But I'm
puzzled about
how to implement the initWithCoder: method.
Suppose I have this in MyClass.h:
NSString *S1, *S2, *S3;
and this in its init function:
S1 = @"a string";
S2 = [[NSString alloc] init];
S3 = [NSString string];
So to conform to the protocol, I'd have something like this in
MyClass.m
too:
In addition to the replies I want to give a hint to something else:
- (id)initWithCoder:(NSCoder *)decoder {
self = [super init];
This is only correct, if your base class does not support NSCoding.
Otherwise you have to call -initWithCoder: (super).
Because this depends of the base class, we have a fragile base class
problem. (Adding NSCoding to the base class looks like doing
everything
correct inside the base class, but will cause MyClass as a subclass
to a
malfunction.) Keep in mind, that NSCoding can be added through a
category.
So it looks safer to do:
if( [super respondsToSelector:@selector( initWithCoder: )] {
self = [super initWIthCoder:decoder];
} else {
self = [super init];
}
No, this will not work. Unless you've implemented -respondsToSelector:
yourself, [super respondsToSelector:] and [self respondsToSelector:]
will always return the exact same value (because they call the exact
same method).
Yup, you are complelty right. The correct code:
if( [BaseClass
instancesRepondsToSelector@selector( initIWithCoder: )] ) {
…
Sorry for that!
Cheers
I never had this problem in practice, but theoretically … (But
maybe I got a
paranoia.)
Cheers
S1 = [decoder decodeObjectForKey:@"S1"];
S2 = [[decoder decodeObjectForKey:@"S2"] retain];
S3 = [[decoder decodeObjectForKey:@"S3"] retain];
return self;
}
(I'm not posting the encodeWithCoder: method.)
So finally, my question: am I right to retain S2 and S3, and not S1?
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Amin Negm-Awad
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--
Clark S. Cox III
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Amin Negm-Awad
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