Re: NSMutableDictionary or Custom Object when adding properties?
Re: NSMutableDictionary or Custom Object when adding properties?
- Subject: Re: NSMutableDictionary or Custom Object when adding properties?
- From: Ken Thomases <email@hidden>
- Date: Fri, 17 May 2013 01:35:58 -0500
On May 17, 2013, at 1:18 AM, Trygve Inda wrote:
>> On May 17, 2013, at 12:43 AM, Trygve Inda wrote:
>>
>>> The trouble comes in the fact that I need to be able to add properties at
>>> runtime. For the dictionary option, it is easy - just make sure the key
>>> names don't collide and I can add more keys to each dictionary.
>>>
>>> But for the objects I don't see a nice way to do this
>>>
>>> There is setValue:forUndefinedKey: and then each object could keep a local
>>> dictionary of these "defined at runtime" keys.
>>
>> That seems "nice" enough to me. The trick is that the custom class has to be
>> sure to only modify the properties via KVC on itself, not the dictionary, in
>> order to maintain KVO compliance. Another way to put it is that only
>> -setValue:forUndefinedKey: should ever mutate the dictionary (and it should
>> only be invoked by the KVC machinery itself).
>
> Will that work right if I have an NSTableView and one of the columns has a
> binding to "myCustomProperty" (which is not defined in the object model)...
> Will it get sent:
>
> [someObject setValue:someValue forUndefinedKey:myCustomProperty]
>
> Rather than:
>
> [someObject setMyCustomProperty:someValue];
Bindings use KVC. They will do:
[someObject setValue:someValue forKey:@"myCustomProperty"];
The KVC machinery is what will eventually call [someObject setValue:someValue forUndefinedKey:@"myCustomProperty"] for the dynamic properties. (For the predefined properties, it will invoke your setter methods.)
> On disk the data will be stored in a plist and an array of NSDictionaryies
> (some of the key will be required and predefind) but some will be user
> defined.
>
> When I load the data from disk if I use dictionary obejects, I don't have to
> do anything else but if I use custom objects I would have to create them and
> send
>
> [someObject setValue:someValue forUndefinedKey:myCustomProperty]
>
> To each object.
>
> Right?
You can use -setValuesForKeysWithDictionary: to set all of the properties of your object from a dictionary. That uses KVC on each key-value pair, so it works like I described above for bindings.
That said, you should consider doing proper keyed archiving of your class. Don't forget the limits of property lists.
Regards,
Ken
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