On Aug 19, 2009, at 4:28 PM, Gideon King wrote:
So do I need to override hash too? If so, are there any
recommendations as to how to determine the hash easily?
If you need to override -isEqual: to provide something besides pointer
comparison, you should also override -hash. If objects are equal,
their hashes must be equal or you may trigger undefined behaviour in
who knows what situations.
While this may not offer the best performance, the easiest way to
implement -hash would be to take all the properties/internal state of
your object that affect equality, format them into an NSString, and
then return the hash of the string.
E.g.:
- (NSUInteger)hash {
NSString* valueRepresentation = [NSString stringWithFormat:@"%@ %lu",
self.companyName,
self.departmentID];
return [valueRepresentation hash];
}
hope this helps,
-natevw
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