Mapping string to UUID in go

Question

I'm using mitchellh/mapstructure to map from map[string]interface{} to struct

Is there any way to tell mapstructure to convert string to uuid.UUID ?

map[string]interface{} :

{
    "id": "af7926b1-98eb-4c96-a2ba-7e429085b2ad",
    "title": "new title",
}

struct

package entities

import (
    "github.com/google/uuid"
)

type Post struct {
    Id      uuid.UUID  `json:"id"`
    Title   string     `json:"title"`
}

Answer 1

You could add a DecodeHookFunc :

func decode(input, output interface{}) error {
    config := &mapstructure.DecoderConfig{
        DecodeHook: mapstructure.ComposeDecodeHookFunc(
            stringToUUIDHookFunc(),
        ),
        Result: &output,
    }

    decoder, err := mapstructure.NewDecoder(config)
    if err != nil {
        return err
    }

    return decoder.Decode(input)
}

func stringToUUIDHookFunc() mapstructure.DecodeHookFunc {
    return func(f reflect.Type, t reflect.Type, data interface{}) (interface{}, error) {
        if f.Kind() != reflect.String {
            return data, nil
        }
        if t != reflect.TypeOf(uuid.UUID{}) {
            return data, nil
        }

        return uuid.Parse(data.(string))
    }
}

• Source: https://github.com/mitchellh/mapstructure/issues/236
• Documentation: https://pkg.go.dev/github.com/mitchellh/mapstructure#DecodeHookFunc