Allow types to determine how to decode themselves

[mthjs]

When the destination of a decode implements the custom decoder interface, use said interface. Custom decoders take precedence over the default decoding rules.

This should resolve https://github.com/mitchellh/mapstructure/issues/115

Renamed the master -> main which closed the pull-request, sorry :sweat_smile:

[wrouesnel]

I'd like to see this merged, though to offer one comment, the interface function - Decode() might be a bit too generic within the go-ecosystem? MapStructureDecode maybe?

[andig]

+1 for allowing objects to decode themselves.

[mthjs]

@wrouesnel I've applied your suggestion although I did swap the order. Like any of the standard-libraries UnmarshalX functions, I've opted to suffix the expected Decode function with Mapstructure instead of prefixing it.

[stephen-slm]

@mitchellh any interest in this being merged?

[dplepage-dd]

Would it be possible to make this work in both directions, so that e.g. decoding a Someone into an interface{} produces a string (the same way json allows customizing both MarshallJSON and UnmarshallJSON)?

There would be some ambiguity, I guess, since you could conceivably call Decode(x,y) with x and y both being types with custom encoder/decoders, but in practice I think it's rarely used as a generic converter, it's almost always either decoding from a map structure to a custom type or encoding from a custom type back to a map structure, so it would probably be fine to just error out in case of conflicting custom handlers.

[pcfreak30]

Bumping this b/c this would probably simplify my code a lot to use stdlib marshal interfaces and only 1 hook for it all.

[buzzdan]

@pcfreak30 @mitchellh any updates on this one ?