Subject: Re: Is "-init" really needed?




> Le 10 août 2017 à 16:09, Charles Srstka <[email protected]> a écrit :
>
>> On Aug 10, 2017, at 8:59 AM, Alastair Houghton
>> <[email protected]> wrote:
>>
>> On 10 Aug 2017, at 14:57, [email protected]
>> <mailto:[email protected]> wrote:
>>>
>>> On Aug 10, 2017, at 02:18, Alastair Houghton <[email protected]>
>>> wrote:
>>>>
>>>> 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
>> constructors.
>>
>> Kind regards,
>> ...


>> Alastair.
>
> 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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