Re: NSDictionary trouble
Re: NSDictionary trouble
- Subject: Re: NSDictionary trouble
- From: Kyle Sluder <email@hidden>
- Date: Tue, 19 Jan 2010 15:18:19 -0800
On Tue, Jan 19, 2010 at 3:09 PM, Shawn Rutledge
<email@hidden> wrote:
> Well yeah, that's one of the reasons java.lang.String is immutable.
> But it helps that java.lang.Object has both hashCode and equals, so
> any object can be put into a collection that depends on those... you
> just have the option of improving the implementation of those for
> better hash distribution, comparing two objects by content rather than
> reference location, etc. I just wanted a hashtable that uses keys by
> pointer rather than expecting to copy them. Nice to know that copying
> protocol doesn't mean you have to actually copy it though.
NSObject has -hash and -isEqual:. If you want a pointer-based
dictionary, create a CFDictionary with the appropriate options, and
cast it to NSDictionary* (read the documentation on Toll-Free Bridging
to see why this is possible).
> As for C++, you can use template containers to store either pointers
> or copies of objects, whichever you like.
STL containers are far more explicit about their internal behavior.
It's possible to write a collection class that has the same
restrictions as NSDictionary.
--Kyle Sluder
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