Relationship between -isEqual and -hash
Relationship between -isEqual and -hash
- Subject: Relationship between -isEqual and -hash
- From: "Jeffrey J. Early" <email@hidden>
- Date: Fri, 19 Jan 2007 13:46:01 -0800
Quick question:
It is well stated in the documentation that the following must be true:
If two objects are equal (as determined by the isEqual: method),
they must have the same hash value.
My question is whether the reverse must also hold?
I assume because it's not mentioned in the documentation (and I can't
think of a reason why), it must be okay.... but that isn't
necessarily good reasoning :-)
In my code I have a dictionary that I want to behave in a particular
way. I'm using objects as keys where if two objects are 'close
enough', they will return the same value from the dictionary, even if
these objects aren't equal in the -isEqual: sense. So when objects
are 'close enough', I have them return the same hash value.
thanks for your help,
Jeffrey
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