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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