Re: Where is NSList?
Re: Where is NSList?
- Subject: Re: Where is NSList?
- From: Matt Freels <email@hidden>
- Date: Tue, 27 Jul 2004 17:48:13 -0500
What about NSSet?
From Documentation:
"Use sets as an alternative to arrays when the order of elements isnt
important and performance in testing whether an object is contained in
the set is a consideration. While arrays are ordered, testing them for
membership is slower than testing sets."
On Jul 27, 2004, at 5:35pm, Tim Conkling wrote:
Sorry, I think I was pretty unclear in my original post.
I'm looking for a container that returns some information that
uniquely identifies each object added to it. This information is
called an iterator in the STL, but it's not used exclusively for
iterating over a container of objects, and I'm not actually looking to
iterate over a list of objects here. These iterators allow for
bidirectional reference between the list and the objects in the list
-- i.e., the list knows which objects it contains; and each object, if
it chooses to retain the iterator returned to it by the list it is
added to, knows exactly where it is contained in the list.
This is very useful, because it allows for operations like deletion
(which take linear time in a container like an NSArray) to be done in
constant time (in a list container), if you have retained the iterator
for the object to be deleted. Importantly, these iterators remain
valid when the container is modified.
An array is good for quick access via index, but object lookup is
slow. If I have an object that I know is contained in an NSArray, and
I want to delete it from that array, there is no quick method of doing
so -- the operation is necessarily performed in linear time, AFAIK.
Again, I'm new to Cocoa, so I may be missing something, but I have
already looked at the documentation for NSArray and NSEnumerator, and
they don't seem to provide the functionality I'm looking for. But I
certainly apologize if I'm missing something obvious.
Thanks,
Tim
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