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Re: Zeroing out instance variables
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Re: Zeroing out instance variables


  • Subject: Re: Zeroing out instance variables
  • From: Ken Thomases <email@hidden>
  • Date: Sat, 17 Apr 2010 09:16:08 -0500

On Apr 17, 2010, at 8:53 AM, Paul Sanders wrote:

> Something I've never been clear about though is
> where an object's retain count is stored.  This obviously
> requires an iVar somewhere (in addition to isA), so there might
> be a trap for the unwary there [...]

My understanding, which is vague and for which I have no references, is that it's handled in a manner similar to what was recently exposed via the associated references API (i.e. objc_setAssociatedObject and friends).

That is, retain counts are stored outside of the instance.

Having just looked up the source for CFRelease, I can't say my understanding has increased.  ;)  Although, there is confirmation there that the retain count is at least sometimes held externally.

Would be an interesting subject for Mr. Bumgarner to expound upon on his blog.

Cheers,
Ken

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  • Follow-Ups:
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      • From: "Paul Sanders" <email@hidden>
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References: 
 >Zeroing out instance variables (From: Ben Haller <email@hidden>)
 >Re: Zeroing out instance variables (From: Graham Cox <email@hidden>)
 >Re: Zeroing out instance variables (From: Ben Haller <email@hidden>)
 >Re: Zeroing out instance variables (From: "Paul Sanders" <email@hidden>)
 >Re: Zeroing out instance variables (From: Ben Haller <email@hidden>)
 >Re: Zeroing out instance variables (From: "Paul Sanders" <email@hidden>)

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