Re: efficient searching of arrays

FROM : Greg Hurrell
DATE : Mon Aug 14 21:50:16 2006

El 14/08/2006, a las 21:21, Mike Abdullah escribió:

> NSEnumerator *objectsEnumerator = [myArray objectEnumerator];
> MyObject *anObject;
>
> while (anObject = [objectsEnumerator nextObject])
> {
>     if ([anObject objectID] == 204)
>         return anObject;
> }
>
> However this seems a little clunky.  Is there a better way of doing 
> things in Cocoa that I haven't come across?


The code you post is a perfectly legitimate way of searching through 
an array. You could hide some of its verbosity behind a macro 
definition or even a method in a category on NSArray if you wanted. 
There are also examples of enumeration macros out there on the web 
(Google) that you can use to make the enumeration idiom a little more 
compact. And changes in the GCC CVS suggest that Apple will be adding 
a "foreach" keyword in Objective-C 2.0 anyway...

For alternatives you could consider some kind of "higher order 
messaging":

http://cocoadev.com/index.pl?HigherOrderMessaging

Another option, if your objects are key-value coding compliant is to 
leverage the NSArray's valueForKey: and indexOfObject: methods. For 
example, the following one-liner (typed in Mail.app, not checked):

return [myArray objectAtIndex:[[myArray valueForKey:@"objectID"] 
indexOfObject:[NSNumber numberWithUnsigned:204]]]

Note that that won't work if there is an object with that id in your 
array; otherwise the indexOfObject: method will return NSNotFound and 
when you pass that to objectAtIndex: an NSRangeException will be raised.

Now I personally would never use this approach but as an intellectual 
exercise I guess it's possible.

G