Re: Differences between -isEqual: and -isEqualTo:?
Re: Differences between -isEqual: and -isEqualTo:?
- Subject: Re: Differences between -isEqual: and -isEqualTo:?
- From: Jim Correia <email@hidden>
- Date: Thu, 18 Sep 2008 18:12:08 -0400
On Sep 18, 2008, at 5:59 PM, Dave DeLong wrote:
IIRC, isEqual: compares memory addresses, whereas isEqualTo:
compares hashes of the objects being compared. I also believe that
isEqual: is the preferred method.
I don't intend to necessarily single Dave out here, but I can't see
how posting an IIRC answer to the list is in anybody's interest,
especially when it is so easy to check the documentation.
Having a non-authoritative and/or incorrect answer has the potential
for clouding the issue for years to come because it will live on in
the list archives.
Pointer comparison is not, in general, how -isEqual: works. Please
read the documentation.
On Sep 18, 2008, at 3:57 PM, Rick Mann wrote:
I see that NSObject (and its protocol) define -isEqual: and -
isEqualTo:. What's the difference? Why does something like NSArray's
-indexOfObject: use -isEqual: and not -isEqualTo:? So that someone
can redefine these for an existing class? Why does -isEqualTo: even
exist?
-isEqualTo is part of the Cocoa Scripting whose clause evaluation
tests. It is implemented by sending -isEqual: to the receiver, or -
scriptingIsEqualTo: as appropriate. See the documentation for details.
By having a different comparison hook for scripting whose tests, one
could potentially have different scripting equality rules if necessary.
- Jim
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