[swift-evolution] [Proposal] Foundation Swift Archival & Serialization

[Colin Barrett]

On Thu, Mar 16, 2017 at 3:33 PM Itai Ferber via swift-evolution <
swift-evolution at swift.org> wrote:

>
> Here's what I mean: Suppose I have a BlogPost model, and I can both fetch
> and post BlogPosts to a cross-platform web service, and store them locally.
> But when I fetch and post remotely, I ned to conform to the web service's
> formats; when I store an instance locally, I have a freer hand in designing
> my storage, and perhaps need to store some extra metadata. How do you
> imagine handling that sort of situation? Is the answer simply that I should
> use two different types?
>
> This is a valid concern, and one that should likely be addressed.
>
> Perhaps the solution is to offer a userInfo : [UserInfoKey : Any] (
> UserInfoKey being a String-RawRepresentable struct or similar) on Encoder
> and Decoder set at the top-level to allow passing this type of contextual
> information from the top level down.
>

I assumed that in those situations, one would create a wrapper struct,

struct WebBlogModel {
    let wrapped: BlogModel
}

probably for the encoding impl that requires more custom work. The
implementation of Codable for this struct would then serialize
(deserialize) from (to) its wrapped value's properties directly.

Types already provide a means for performing context sensitive
implementation selection, I don't think it's necessary to provide another
way to do that in Swift. Of course I could very well be wrong :)

-Colin
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