+1 this is missing functionality at the moment and what still puts tools like
Mantle ahead.
Sent from my iPhone
> On 19 Dec 2017, at 04:18, Charlie Monroe via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> For me definitely +1 as it's getting near to what I need to call the Decoding
> usable.
>
>> On Dec 18, 2017, at 5:51 PM, Arsen Gasparyan via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>> Hello everyone,
>>
>> I’m suggesting to add a new way to encode/decode JSON properties for
>> relevantly complex data formats such as regular expressions, well-known
>> text, hex colours, custom date formats.
>>
>> The problem:
>>
>> Image you have a struct called House
>>
>> struct House {
>> let color: UIColor
>> }
>>
>> and it has a properly called color and the color represented in JSON as hex
>> value (#ffffff). Currently to make it working you have to extract the
>> underline value (string with a hex value) and then try to make a UIColor
>> from it. It works but it makes you to copy/past a lot of code and it leads
>> to problems. Also it shifts focus from what to decode to how to decode.
>>
>> The suggested solution:
>>
>> I suggest that we have to introduce protocols for classes that will
>> encapsulate transformation from a source data type to a destination data
>> type. The source data types are all existing data that support of decoding.
>>
>> We will provide only protocols (one for decoding and one for encoding) and
>> users will be able to create transformers for their own data types.
>>
>> The implementation:
>>
>> The implementation is fairly easy. We only need introduce two protocols
>> (encoding/decoding) and add a method to KeyedEncodingContainerProtocol that
>> will accept a key and a transformer. In the method we will extract source
>> data from JSON and then will ask the transformer to try to convert it to the
>> desire data type.
>>
>> Example of the decoding protocol:
>>
>> protocol DecodingTransformer {
>> associatedtype Input: Decodable
>> associatedtype Output
>> func transform(_ decoded: Input) throws -> Output
>> }
>>
>>
>> Inspired by: https://github.com/Hearst-DD/ObjectMapper#custom-transforms
>>
>> Cheers,
>> Arsen
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>
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