Re: More Swift issues, NSURLComponents
Re: More Swift issues, NSURLComponents
- Subject: Re: More Swift issues, NSURLComponents
- From: Rick Mann <email@hidden>
- Date: Mon, 12 Oct 2015 14:12:53 -0700
> On Oct 12, 2015, at 14:08 , Jens Alfke <email@hidden> wrote:
>
>
>> On Oct 12, 2015, at 2:00 PM, Rick Mann <email@hidden> wrote:
>>
>> In all this discussion, I forgot to bring up the containers: are they special? A "let" container can't be reassigned, nor can its contents be changed. How is this implemented?
>
> No, they’re not special, but they’re structs (not classes). That means they’re passed by value (copied), and their methods can be marked ‘mutable’ to indicate that they modify the object.
Oh! I thought they were classes. Thanks.
> Under the hood, as an optimization, the collection classes use copy-on-write indirection — an Array struct just contains a pointer to an internal buffer (a class instance) that has the actual data. That makes copying an Array efficient. The implementation just has to be careful to allocate a new buffer before modifying the contents, if the buffer is shared with any other Arrays. (There are some low-level public Swift types that act as helpers for implementing this pattern.)
>
> If you want to know lots more, read Mike Ash’s article “Let’s Build Swift Array”:
> https://www.mikeash.com/pyblog/friday-qa-2015-04-17-lets-build-swiftarray.html
>
Thanks!
--
Rick Mann
email@hidden
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