[macrophyllum]

OK, I am about to release my a new application which encodes instance variables in a model class. Before I release it, I want to make sure that there is backward compatability with saved files, because I am sure in the future I will modify the model class and its encoding and decoding methods. So, someone suggested I use the method encodeObject(id)anObject forKey:(NSString *)str

Here is my encode method:

-(void)encodeWithCoder:(NSCoder *)coder {
//name returns an NSString
[coder encodeObject: [self name] forKey:@"Name"];
//date returns an NSCalendarDate
[coder encodeObject: [self date] forKey:@"Date"];
}

Whenever I save, the first line of code in this method gives the following error:

Exception raised during posting of notification. Ignored. exception: *** -encodeObject:forKey: only defined for abstract class. Define -[NSArchiver encodeObject:forKey:]!

I should say that my model class is a subclass of NSObject and in the hearder I have this:

@interface MyModelClass : NSObject <NSCoding>

Note also that it works fine if I use the method encodeObject, it just throws the exception when I use the encodeObject forKey.

So, excuse my ignorance, but how do I "define" NSArchiver encodeObject:forKey: ?

~Thanks

[Ghoser777]

Tada:

http://developer.apple.com/techpubs/...ngobjects.html


Matt

[macrophyllum]

Thanks Matt. I have read over that documentation, I get an error if I call super encodeObject forKey...

I put in the if conditional and when it saves it never uses the encodeObject: forKey: path.

According to the documentation I don't need the if conditional: "If instances of your class can only be encoded to an keyed archive, you can omit the section that encodes values using the nonkeyed methods."

So I figure this is my case, but I still get the "define..." exception.

Any other suggestions?

[Ghoser777]

Are you using NSArchiver to enode or your object? That might be your problem.

Matt

[macrophyllum]

I am not using NSArchiver to encode each instance of my object. Can you post an example of how I would do that?

[Ghoser777]

I'd simply be copying pasting the example in Apple's docs. Could you post your code? That would be easier to debug. Skeleton code is alright.

Matt

[macrophyllum]

OK, here is my encode method, which definitely gets called when I save. If I try this, I get the exception error posted above.

-(void)encodeWithCoderNSCoder *)coder {

[coder encodeObject: [self returnStringMethod] forKey:@"ItemA"];

[coder encodeObject: [self date] forKey:@"Date"];
[coder encodeObject: [self notes] forKey:@"Notes"];

[coder encodeInt:anInt forKey:@"IntOne"];

[coder encodeFloat:aFloat forKey:@"FloatOne"];

}

[Ghoser777]

Well, I guessed that. What are you calling to encode your object? That was the code I was hoping you would post in addition (sorry this is taking so long).

Matt

[macrophyllum]

Don't apologize, I am just glad someone is looking at the code and trying to help.

I hope this is what you want.

I store instances of my model class myModelClass in an NSMutableArray. In another class which is a subclass of NSDocument, I override, dataRepresentationOfType where I then store my NSMutableArray into an NSMutableDictionary and then I call:

return [NSArchiver archivedDataWithRootObject:eventDict];
//eventDict is the mutable dict.

[Ghoser777]

Oh, so you ARE using NSArchiver to archive your object. That would have cleared this up sooner. NSArchiver doesn't support keyed archiving; use NSKeyedArchiver instead.

There you go,
Matt

[macrophyllum]

Thanks Matt! It works.

So do you think if I release a new version I can just encode any new instance variables with new keys and decode them with the new keys? Do you think it will be that easy?

[Ghoser777]

For new objects, yep. It's slightly more code if your application every wrote out data without using keyed archiving, but if this is a new object, then go keyed archiving all the way and it really should be that simple.

Matt