Go – function for converting a struct to map in Golang

go

I want to convert a struct to map in Golang. It would also be nice if I could use the JSON tags as keys in the created map (otherwise defaulting to field name).

Edit Dec 14, 2020

Since structs repo was archived, you can use mapstructure instead.

Edit TL;DR version, Jun 15, 2015

If you want the fast solution for converting a structure to map, see the accepted answer, upvote it and use that package.

Happy coding! 🙂

Original Post

So far I have this function, I am using the reflect package but I don't understand well how to use the package, please bear with me.

func ConvertToMap(model interface{}) bson.M {
    ret := bson.M{}

    modelReflect := reflect.ValueOf(model)

    if modelReflect.Kind() == reflect.Ptr {
        modelReflect = modelReflect.Elem()
    }

    modelRefType := modelReflect.Type()
    fieldsCount := modelReflect.NumField()

    var fieldData interface{}

    for i := 0; i < fieldsCount; i++ {
        field := modelReflect.Field(i)

        switch field.Kind() {
        case reflect.Struct:
            fallthrough
        case reflect.Ptr:
            fieldData = ConvertToMap(field.Interface())
        default:
            fieldData = field.Interface()
        }

        ret[modelRefType.Field(i).Name] = fieldData
    }

    return ret
}

Also I looked at JSON package source code, because it should contain my needed implementation (or parts of it) but don't understand too much.

Best Answer

I also had need for something like this. I was using an internal package which was converting a struct to a map. I decided to open source it with other struct based high level functions. Have a look:

https://github.com/fatih/structs

It has support for:

  • Convert struct to a map
  • Extract the fields of a struct to a []string
  • Extract the values of a struct to a []values
  • Check if a struct is initialized or not
  • Check if a passed interface is a struct or a pointer to struct

You can see some examples here: http://godoc.org/github.com/fatih/structs#pkg-examples For example converting a struct to a map is a simple:

type Server struct {
    Name    string
    ID      int32
    Enabled bool
}

s := &Server{
    Name:    "gopher",
    ID:      123456,
    Enabled: true,
}

// => {"Name":"gopher", "ID":123456, "Enabled":true}
m := structs.Map(s)

The structs package has support for anonymous (embedded) fields and nested structs. The package provides to filter certain fields via field tags.

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