On Mar 10, 2009, at 2:33 PM, Тимофей Даньшин wrote:
I am writing a method for searching for the longest common
substring. The idea is to store the pieces of that LCS in an
NSMutableDictionary with TMIntWrappers as keys and NSMutableStrings
as values.
Now, TMIntWrapper is the class i created for wrapping ints into
objects. It stores an int, gives access to it via the .value
property, adopts the NSCopying protocol and implements the -(BOOL)
isEqual: (id) object method.
Does TMIntWrapper also implement -hash? And is the .value property
mutable?
<http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Protocols/NSObject_Protocol/Reference/NSObject.html
>
If two objects are equal (as determined by the isEqual: method),
they must have the same hash value. This last point is particularly
important if you define hash in a subclass and intend to put
instances of that subclass into a collection.
If a mutable object is added to a collection that uses hash values
to determine the object’s position in the collection, the value
returned by the hash method of the object must not change while the
object is in the collection. Therefore, either the hash method must
not rely on any of the object’s internal state information or you
must make sure the object’s internal state information does not
change while the object is in the collection. Thus, for example, a
mutable dictionary can be put in a hash table but you must not
change it while it is in there. (Note that it can be difficult to
know whether or not a given object is in a collection.)
And, as others have asked, can you use NSNumber?
--Andy
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