Since mutable arrays and dictionaries expand as required when new
objects are added, when should one use -initWithCapacity: methods?
I'd guess they're only worth using if you know you are about to
populate one with a lot of items and the performance hit of letting
them grow "naturally" is worth avoiding. There may also be private
classes within the cluster that are optimised for certain numbers of
objects, so this will act as a hint as to which one should be used.
My suggestion would be to never use the "-initWithCapacity:" methods
unless you know that you have a good reason for using them. I would
expect that in at least 99% of the times that you use collections
there is no measurable difference in performance between using "-
initWithCapacity:" over regular "-init".
Some general suggestions for best practices wrt. optimizations:
1) Measure first
2) Implement supposed optimization
3) Measure to see the impact of the code change
4) Based on the result of #3, either scrap your changes, or document
the optimized code
Skipping over step #1 and #3 is always a mistake - It's almost always
the case that you'll end up surprised by what you find! We also often
forget to do #4, something that typically leads to maintenance
problems later on.
j o a r
_______________________________________________
Cocoa-dev mailing list (email@hidden)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
