Re: When do I need to override hash?
Re: When do I need to override hash?
- Subject: Re: When do I need to override hash?
- From: David Duncan <email@hidden>
- Date: Thu, 20 Aug 2009 12:33:28 -0700
On Aug 20, 2009, at 12:00 PM, Seth Willits wrote:
Returning 0 is certainly simpler :p
It is, but you can generally do better than just returning 0, usually
by just extracting some bits from 'self', ala
-(NSUInteger)hash
{
uintptr_t hash = (uintptr_t)self;
return (hash >> 4);
}
This satisfies the condition of hash (two equal objects will have the
same hash code) without relying on object state (since a particular
object's location in memory will never change). You can probably do
even better than this, but as with hash codes in general there is a
certain amount of experimentation required.
--
David Duncan
Apple DTS Animation and Printing
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