Re: Nil items in NSMutableSet
Re: Nil items in NSMutableSet
- Subject: Re: Nil items in NSMutableSet
- From: Steven Degutis <email@hidden>
- Date: Tue, 16 Mar 2010 19:22:44 -0400
Daniel,
Method swizzling is fine for debugging purposes, but should not be used in
production code. This has already been said by some people who really,
really know what they're talking about.
And it's *very* dangerous to swizzle something on NSString. The first reason
(of many) that comes to mind, is that most of Apple's own internal
Objective-C frameworks are using NSStrings, in ways and situations you can't
predict. So by advising someone to mess with NSString's implementation, you
are advising them to potentially break their app in countless ways (possibly
even data-corrupting ones) and then send that app to unsuspecting users. Not
a great piece of advise, in my book.
-Steven
On Tue, Mar 16, 2010 at 6:34 PM, Daniel DeCovnick <email@hidden> wrote:
> There was a thread on this list a few days ago about effective method
> swizzling into Apple classes. Despite being replete with warnings about
> "Don't use it in production code," it IS doable, and very, very cool, IMHO.
>
> -Dan
>
>
> On Mar 16, 2010, at 2:18 PM, Alejandro Rodriguez wrote:
>
> You were right, my equality is not transitive.
>>
>> id ob = [[objectClass alloc] initWithId:@"hello"];
>> [ob isEqual:@"hello"]; //returns YES
>> [@"hello" isEqual:ob]; //returns NO
>>
>> That may very well be the problem... now... I have no idea on how I will
>> make the second test return YES.
>>
>> doesn't that depend on the implementation of isEqual of the asking object
>> in this case NSString? Have any of you had to deal with this before? I'll
>> dive into the docs and see what details I find that might be useful.
>>
>> Seems we are getting somewhere
>> cheers!
>>
>> Alejandro
>>
>> On Mar 16, 2010, at 2:45 PM, Clark Cox wrote:
>>
>> On Tue, Mar 16, 2010 at 11:35 AM, Thomas Davie <email@hidden>
>>> wrote:
>>>
>>>> Your code doesn't account for the possibility that the order of
>>>>> comparison might happen in the other order (i.e. [@"123" isEqual:
>>>>> object]). I wouldn't be surprised if NSSet is assuming that equality
>>>>> is transitive (i.e. [a isEqual: b] == [b isEqual: a]).
>>>>>
>>>>
>>>> For reference, this property is not transitivity, the transitivity
>>>> relation is:
>>>>
>>>> a -> b ^ b -> c => a -> c (for some relation ->)
>>>>
>>>> The one you're looking for is commutativity.
>>>>
>>>
>>> Indeed; must have been echos of my previous life as a C++ programmer
>>> creeping into the Obj-C part of my brain (in C++, the std::set class
>>> uses less than, instead of equality, where transitivity is the
>>> important property, not commutativity).
>>>
>>> :)
>>>
>>>
>>>
>>> --
>>> Clark S. Cox III
>>> email@hidden
>>>
>>
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--
Steven Degutis
http://www.thoughtfultree.com/
http://www.degutis.org/
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