> Le 10 août 2017 à 16:09, Charles Srstka <cocoa...@charlessoft.com> a écrit :
>> On Aug 10, 2017, at 8:59 AM, Alastair Houghton
>> <alast...@alastairs-place.net> wrote:
>> On 10 Aug 2017, at 14:57, gerti-cocoa...@bitart.com
>> <mailto:gerti-cocoa...@bitart.com> wrote:
>>> On Aug 10, 2017, at 02:18, Alastair Houghton <alast...@alastairs-place.net>
>>>> Personally I *would* still discourage +new in favour of class-specific
>>>> convenience constructors because I think it’s less expressive and also
>>>> less consistent (e.g. +array is better, in my opinion, than +new, not
>>>> least because +arrayWithObjects: and others exist).
>>> [NSArray new] := [[NSArray alloc]init]
>>> [NSArray array] := [[[NSArray alloc]init]autorelease]
>>> +array and friends came along with the introduction of autorelease pools,
>>> to replace +new with something that didn't imply ownership (the oft
>>> mentioned special meaning of "new" as prefix). So while with ARC they are
>>> essentially equivalent, previously they were not.
>> Yes, I know that, thanks.
>> The point is, with ARC, they’re equivalent, and most new code uses ARC, so,
>> again, I’d discourage +new in favour of class-specific convenience
>> Kind regards,
> They’re equivalent syntactically, but performance-wise, +array and friends
> will cause the object to be put into an autorelease pool. Therefore, +new is
> better for performance.
Putting an object into an autorelease pool is very cheap. It is just a write of
the pointer value in a thread local array. When using ARC, the object is still
pushed in the autoreleased stack, but it may be immediately pop by the caller.
So yes, +array still have a couple of additional operations to perform, but it
should be mesure to tell if this is significant performance wise.
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