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Re: File Extensions Problem
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Re: File Extensions Problem


  • Subject: Re: File Extensions Problem
  • From: Graham Cox <email@hidden>
  • Date: Fri, 29 Aug 2008 10:12:30 +1000


On 29 Aug 2008, at 4:28 am, Ken Thomases wrote:

On Aug 27, 2008, at 5:59 PM, R.L. Grigg wrote:

Hmm, I guess the wrinkle in this particular case is if the "contract" doesnt specify something that the programmer assumes to be safe to do (like enumerating backwards), how can you know how to implement your end?

Enumerating NSArrays backwards is safe and supported by the framework. The earlier discussion had to do with mutating a collection while enumerating, which is explicitly stated to be unsafe. Somebody (I forget who) claimed that mutating was "safe" while enumerating backwards, but they were wrong. In this case, their wrongness was not based on things left unsaid in the contract, but on violating things explicitly laid out in the contract.


Well, that was me. But I do see the error of my ways... I guess it was Michael Ash's comment that NSArray *could* change its storage half way through enumeration (if the collection were mutated) that woke me up. I suspect it would only do this if the collection dramatically changed in size but clearly that wouldn't be something to rely on. I checked my own code to make sure I wasn't following my own "advice" anywhere and turns out I've never done it without making a copy anyway.

cheers, Graham
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  • Follow-Ups:
    • Re: File Extensions Problem
      • From: Uli Kusterer <email@hidden>
References: 
 >File Extensions Problem (From: Adil Saleem <email@hidden>)
 >Re: File Extensions Problem (From: Michael Dautermann <email@hidden>)
 >Re: File Extensions Problem (From: Andrew Merenbach <email@hidden>)
 >Re: File Extensions Problem (From: Graham Cox <email@hidden>)
 >Re: File Extensions Problem (From: Phil <email@hidden>)
 >Re: File Extensions Problem (From: Graham Cox <email@hidden>)
 >Re: File Extensions Problem (From: "Michael Ash" <email@hidden>)
 >Re: File Extensions Problem (From: Thomas Engelmeier <email@hidden>)
 >Re: File Extensions Problem (From: "R.L. Grigg" <email@hidden>)
 >Re: File Extensions Problem (From: Ken Thomases <email@hidden>)
 >Re: File Extensions Problem (From: "R.L. Grigg" <email@hidden>)
 >Re: File Extensions Problem (From: Ken Thomases <email@hidden>)

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