# Automatic Codable conformance for enums with associated values that themselves conform to Codable

**URL:** <https://forums.swift.org/t/automatic-codable-conformance-for-enums-with-associated-values-that-themselves-conform-to-codable/11499>\
**Category:** Pitches\
**Created:** [March 30, 2018, 12:39am UTC](https://forums.swift.org/t/automatic-codable-conformance-for-enums-with-associated-values-that-themselves-conform-to-codable/11499 "2018-03-30T00:39:03Z")\
**Posts on this page:** 1\
**Showing post:** 13

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**Author:** ![itaiferber](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/itaiferber/32/33840_2.png) [@itaiferber](https://forums.swift.org/u/itaiferber)\
**Post date:** [May 14, 2018, 7:23pm UTC](https://forums.swift.org/t/automatic-codable-conformance-for-enums-with-associated-values-that-themselves-conform-to-codable/11499/13 "2018-05-14T19:23:28Z")

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Apologies — I wrote the above while in a bit of a hurry, so let me clarify: I don't think one use case is more important than another; I think we should find a solution which is able to synthesize code for both use cases which want a discriminator, and those which do not.

For instance, one straw-man approach to this is to generate both implementations and allow someone to use either approach via a property, e.g.

```swift
enum SynthesizedEnumDiscriminatorType {
    // No discriminator -- attempt cases in order single-value
    case none

    // Use the case name as the value-containing key, e.g.
    // {"album": {"id": "abc"}} or {"podcast": {"id": "xyz"}}
    case discriminateByCaseName

    // Use the case name as a discriminator keyed by the given key, e.g.
    // with disciminateByCaseNameForKey(CodingKeys.object), {"object": "album", "id": "abc"}
    case discriminateByCaseNameForKey(CodingKey)
}

enum MyEnum {
    case string(String)
    case double(Double)

    // Synthesized
    static var codableDiscriminatorType: SynthesizedEnumDiscriminatorType {
        return .none
    }

    init(from decoder: Decoder) throws {
        switch MyEnum.codableDiscriminatorType {
            // ... use the strategies
        }
    }
}

```

Essentially, add another customization point by using a property similar to how `CodingKeys` influences the representation of a structured type. If you want to override the discriminator strategy used, provide a discriminator type via the enum (you can even make it mutable if we decide to generate all implementations and choose dynamically).

* * *

Of course, there are design issues with the above, but what I'm trying to get at is that it's possible to come up with solutions that work across multiple use cases.

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