[swift-users] Is there any way to decode from Any type JSON Object using JSONDecoder?

[Tony Parker]

Hi Masaki,

Do you mean that you are going through the JSON as a string value and changing the keys, then you want to pass this re-written JSON to the decoder?

- Tony

> On Jun 21, 2017, at 6:58 PM, Masaki Haga via swift-users <swift-users at swift.org> wrote:
> 
> Hi Swift-Users,
> 
> I was wondering if there is any way to decode JSON from Any type JSON Object using `JSONDecoder`, not from Data type object. 
> 
> Currently, `JSONDecoder` has only one decode function which decodes Data type object to `Decodable`. Inside the function, it serializes Data object to Any Type JSON Object using `JSONSerialization` and pass it into `_JSONDecoder(referencing:, options:)` (Refer JSONEncoder.swift#874).
> 
> As discussed in some of other threads such as "SE-0166: Swift Archival & Serialization", the default implementation of JSONDecoder or Decodable protocol doesn’t allow to decode from one format to another format (such as snake-case to camel-case), we need to implement custom CodingKey enums. However, in our project, to parse the server API JSON response with snake-case, declaring custom CodingKey enums for all the pre-existing models is almost impossible and very inefficient, so I decided to covert all the JSON keys from snake-case to camel-case, and then pass it into `JSONDecoder.decode`. To achieve this, we need to convert the Data object resulted from `URLSession.task` to Any type JSON Object using `JSONSerialization`, do the conversion from snake-case to camel-case and then convert back to Data type and then pass to `JSONDecoder.decode` which looks very redundant because the function uses `JSONSerialization` inside of it as mentioned above. If there is a function like below, we can get rid of this redundant call of `JSONSerialization`.
> 
> ```
> func decode<T : Decodable>(_ type: T.Type, from JSONObject: Any) throws -> T
> ```
> 
> Sorry if I am misunderstanding the new API but is there any way to decode `Decodable` directly from Any type JSON Object?
> 
> If not, I think adding the function aforementioned and giving an ability to opt-out this JSON serialization call would give more flexibility to the API in my humble opinion.
> 
> Thank you for reading.
> 
> All the best,
> - Masaki
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20170622/4206e91e/attachment.html>