Json

Create Custom JSON Decoders in Elm 0.18

Published January 13, 2017 · 4 Minute Read · ∞ Permalink

You’ve modeled your data exactly how it should be, and everything’s working fine. Now it’s time to finish your JSON Decoder, but certain fields are strings where in your Elm code they’re complex data types! This happens most often with dates, but tagged unions have this problem too.

In 0.17 we had customDecoder, which could turn any Result String a into a Decoder a, but it went away in 0.18. So… what do we do?