[swift-users] dealing with heterogenous lists/dictionary with Codable

David Sweeris davesweeris at mac.com
Thu Oct 19 15:20:51 CDT 2017

I think if you can figure that out, you’re halfway to letting protocols conform to themselves.

(Syntactically, I would probably say that something like “Codable.Self” would read well, but I think that already means something. Maybe the answer will become clearer when we rework the reflection APIs?)

Sent from my iPhone

> On Oct 19, 2017, at 13:13, Itai Ferber <iferber at apple.com> wrote:
> Even then, that wouldn’t necessarily help in the general case. If you decode {"key" : 1} as [String : Codable], what concrete type would 1 have? Int? Double? Int8? (Arguments can be made for any one of these, but the key here is that it is inherently ambiguous and there isn’t necessarily a good answer.)
> On 19 Oct 2017, at 12:57, David Sweeris wrote:
> On Oct 19, 2017, at 12:50 PM, David Baraff via swift-users <swift-users at swift.org> wrote:
> Yes; this is a case where anywhere in the code base I want to just say
> struct MyNewType : Codable {
> // add codable datatypes
> }
> and don’t want/can’t always go to the centralized place to add it in.
> Is there some extension-like trick I can pull off that lets me spread the implementation out over different files/libraries?
> Ah, ok.
> No, I don't think you'll be able to do that until/unless Swift gets more macro/metaprogramming features. Maybe if protocols ever get to conform to themselves? That's a common request, but implementing it is apparently beyond tricky. I'm pretty sure somebody's working on it, but "bigger fish" and all that...
> - Dave Sweeris
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