Re: NSInvalidArgumentException : can't send message to abstract object
Re: NSInvalidArgumentException : can't send message to abstract object
- Subject: Re: NSInvalidArgumentException : can't send message to abstract object
- From: Aram Greenman <email@hidden>
- Date: Fri, 26 Apr 2002 14:13:07 -0700
On 4/26/02 9:09 AM, "Erik M. Buck" <email@hidden> wrote:
>
NSData is a class cluster. That makes it more difficult to subclass. Apple
>
provides excellent documentation on the subject.
>
>
You are awar that you do not need to create your own GUIDs aren't you.
>
>
See CFUUID: used to produce universally unique 16-byte identifiers
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See [NSProcessInfo globallyUniqueString]
>
I was actually _not_ aware of that. I am really only using a quasi-GUID,
anyway (certain bytes are tagged), but this is useful to know.
Thanks to all who responded!
Aram
>
>
>
----- Original Message -----
>
From: "Aram Greenman" <email@hidden>
>
To: "cocoa-dev" <email@hidden>
>
Sent: Friday, April 26, 2002 1:08 AM
>
Subject: NSInvalidArgumentException : can't send message to abstract object
>
>
>
> I know this has to SO DUMB, but I have racked my brain and the docs --
>
>
>
> here's the offending code:
>
>
>
> @interface GUID : NSData {
>
> }
>
>
>
> + (GUID *)guid;
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> @end
>
>
>
> @implementation GUID
>
>
>
> + (GUID *)guid {
>
>
>
> unsigned char buffer[16];
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>
>
> // guid is generated and stored in buffer
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>
>
> return [self dataWithBytes:buffer length:16];
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> }
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> @end
>
>
>
> when I call [GUID guid], I get this exception:
>
>
>
> *** Uncaught exception: <NSInvalidArgumentException> *** initialization
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> method -initWithBytes:length:copy:freeWhenDone:bytesAreVM: cannot be sent
>
to
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> an abstract object of class GUID: Create a concrete instance!
>
>
>
> Doesn't +dataWithBytes:length: create a concrete instance with +alloc ?
>
(Of
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> course the answer must be "no", otherwise this would work) What's up?
>
> Thanks,
>
>
>
> Aram
>
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>
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