Re: Encode a 'Class' type using NSValue
Re: Encode a 'Class' type using NSValue
- Subject: Re: Encode a 'Class' type using NSValue
- From: Billy Flatman <email@hidden>
- Date: Fri, 14 May 2010 10:45:57 +0100
Hi Quincey,
Thanks for you help. I am trying to pass the class reference around for drag and drop, I think i'll try your idea of converting the pointer to a number,
Cheers,
Billy.
On 14 May 2010, at 10:34, Quincey Morris wrote:
> On May 14, 2010, at 02:13, Billy Flatman wrote:
>
>> I'm trying to encode a 'Class' type parameter in an class implementing the NSCoding interface, but I keep getting the error 'cannot encode (void *) value: <c0860200 01000000>'.
>>
>> Here's an extract the class I'm encoding:
>>
>> @interface IFNode : NSObject <NSCoding> {
>> Class persistentObjectClass;
>> }
>> @property (nonatomic, retain) Class persistentObjectClass;
>> @end
>>
>> @implementation IFNode
>> @synthesize persistentObjectClass;
>> - (void) encodeWithCoder: (NSCoder *) encoder {
>> NSValue* value = [[NSValue valueWithPointer:persistentObjectClass] retain];
>> [encoder encodeObject:value forKey:@"Class"];
>> }
>
> NSValue doesn't support encoding for this sort of value:
>
> http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/Archiving/Tasks/codingctypes.html
>
> What are you really trying to do?
>
> If you're trying to have something persist across uses of your application, it makes no sense to archive the class object pointer. Archive the class name instead (via NSStringFromClass).
>
> If you're just trying to pass the class pointer around within the application (like for dragging or putting something on a private pasteboard), you could probably do it by casting the pointer to a number for encoding, and cast it back to a pointer on decoding, but you're likely still far better off archiving the class name instead.
>
>
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Billy Flatman
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