[swift-users] Protocols, `mutating` and Value vs Reference Types.

[Dave Abrahams]

on Fri Apr 29 2016, Hooman Mehr <hooman-AT-mac.com> wrote:

> Thank you very much for your response. I made the change in the gist. This takes
> me back to the same error that forced my into duplication path:
>
> “Cannot assign through subscript: ‘self’ is immutable” for the object case.
>
> The gist is self contained if you want to compile it yourself.
>
> Is this some kind of bug or the expected behavior?

Looks like a bug to me!

>
>
>     On Apr 29, 2016, at 5:28 PM, Dave Abrahams via swift-users
>     <swift-users at swift.org> wrote:
>
>     on Fri Apr 29 2016, Hooman Mehr <swift-users-AT-swift.org> wrote:
>
>         Hi,
>
>         I am designing APIs that need to support both reference (class/object)
>         and value
>         types. I am running into restrictions of `mutating` keyword in my
>         protocols and
>         this is causing a lot of duplication of code. In order to understand
>         what I mean
>         please take a look at this gist. 
>
>         As you see, I have pairs of almost identical declarations: KeyValueStore
>         vs
>         KeyValueStoreObject, and AnyDictionaryStore vs AnyDictionaryStoreObject.
>         This
>         keeps rapidly growing as I am designing my APIs. Is there any sane way
>         around
>         this?
>
>     protocol KeyValueStoreObject : class, KeyValueStore {}
>     protocol AnyDictionaryStoreObject : class, AnyDictionaryStore {}
>
>     would probably work for you.
>
>     HTH,
>
>     -- 
>     Dave
>
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-- 
Dave