• Open Menu Close Menu
  • Apple
  • Shopping Bag
  • Apple
  • Mac
  • iPad
  • iPhone
  • Watch
  • TV
  • Music
  • Support
  • Search apple.com
  • Shopping Bag

Lists

Open Menu Close Menu
  • Terms and Conditions
  • Lists hosted on this site
  • Email the Postmaster
  • Tips for posting to public mailing lists
Re: File Extensions Problem
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: File Extensions Problem


  • Subject: Re: File Extensions Problem
  • From: "Gerriet M. Denkmann" <email@hidden>
  • Date: Sat, 30 Aug 2008 01:11:32 +0700


On Fri, 29 Aug 2008 12:13:34 -0400, "Michael Ash" <email@hidden> wrote:

On Thu, Aug 28, 2008 at 9:50 PM, Gerriet M. Denkmann <email@hidden> wrote:
While if fully agree with you about valid assumptions and so, I am still
wondering what is the disadvantage of forgetting about NSEnumerator, Fast
Enumeration and the like and simply doing:


unsigned count = [ array count ];
if ( count == 0 ) return;
for( unsigned i = count - 1;; i--)
{
       id a = [ array objectAtIndex: i ];
       if ( a is not nice ) [ array removeObjectAtIndex: i ];
       if ( i == 0 ) break;
}

Maybe not "Fast" as in "Fast Enumeration" but maybe simpler and faster than
copying all the "nice" objects into a secondary array.

The disadvantage is simply that it's more code (and therefore more potential for bugs) and it may be slower.

If performance were not a concern then I'd much prefer something like this:

for(id obj in [NSArray arrayWithArray: array])
    if( condition(obj) )
        [array removeObject:obj];

And if performance is a concern, I'd probably prefer something like this:

NSMutableIndexSet *indexes = [NSMutableIndexSet indexSet];
unsigned index = 0;
for( id obj in array )
{
    if(condition(obj))
        [indexes addIndex:index];
    index++;
}
[array removeObjectsAtIndexes:indexes];

But this is really getting into the realm of personal preference.
Certainly I can't tell you whether this is faster than yours or not,
and the amount of code is such that I wouldn't say that it's
absolutely obvious that it's prettier.

And lastly I just want to note that if your condition fits easily into
an NSPredicate, you can do this whole business as a simple one-liner.

You are right. removeObjectsAtIndexes: is much better than my suggestion. I did not know about this method.
Another thing I should check out is NSPredicate.


Thanks for enlightening me!


Kind regards,

Gerriet.

_______________________________________________

Cocoa-dev mailing list (email@hidden)

Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com

Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden


  • Prev by Date: Re: Checking for memory leaks with Instruments
  • Next by Date: Re: Dynamic right-sizing of TextContainer
  • Previous by thread: Re: File Extensions Problem
  • Next by thread: Re: File Extensions Problem
  • Index(es):
    • Date
    • Thread