[swift-evolution] Idea: Exposing _JSONEncoder and _JSONDecoder functionality

[Morten Bek Ditlevsen]

Thank you so much for the comments Itai and David. Makes perfect sense that
the current implementation could be changed in the future. A stream
implementation would be awesome and sounds like it’s perfectly doable.
A future StructureEncoder has my vote. :-)
Thanks again for the feedback!
Sincerely,
/morten
tir. 25. jul. 2017 kl. 21.08 skrev David Hart <david at hartbit.com>:

> On 25 Jul 2017, at 18:45, Itai Ferber via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Hi Morten,
>
> This is something we’ve considered adding and may do so in the future —
> however, this will require additional API review and will not make it in
> time for the Swift 4.0 release.
> The usage of JSONSerialization as the serialization backend is a current
> implementation detail, and may change in future releases; it would, for
> instance, be more efficient to read/write JSON as we encode/decode, instead
> of trying to collect the entire object graph before performing the next
> step.
>
> As a side note, if this could be pushed even further to allow
> encoding/decoding to/from a Stream, it would allow me to use Codable on a
> project where I’m parsing JSON files in the hundreds of Mbs. I have no
> choice but to use a streaming parser.
>
> We could also introduce something like a general StructureEncoder/
> StructureDecoder which performs this conversion, as this might be useful
> outside of just JSON. (For instance, PropertyListEncoder/
> PropertyListDecoder currently do something similar.)
>
> So yes, this is under consideration for future API. :)
>
> — Itai
>
> On 25 Jul 2017, at 0:44, Morten Bek Ditlevsen via swift-evolution wrote:
>
> In the implementation og JSONEncoder and JSONDecoder we have the internal
> functionality that encodes Codable types to a structure that is compatible
> with JSONSerialization.
> The JSONEncoder then calls JSONSerialization on this structure - and
> JSONDecoder vice versa.
> In some situations it could be nice to just encode or decode to or from
> this structure - and not have the final encoding to Data performed. For
> instance if you have some library that hands you a structure in this format
> and you would like to perform decoding.
>
> Can anyone else see the relevance of exposing this functionality? It could
> be exposed by wrapping _JSONEncoder in a public JSONStructureEncoder or
> something similar.
>
> Sincerely,
> /morten
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