[enums] What is an idiomatic way of representing enums in Go?

It's true that the above examples of using const and iota are the most idiomatic ways of representing primitive enums in Go. But what if you're looking for a way to create a more fully-featured enum similar to the type you'd see in another language like Java or Python?

A very simple way to create an object that starts to look and feel like a string enum in Python would be:

package main

import (
    "fmt"
)

var Colors = newColorRegistry()

func newColorRegistry() *colorRegistry {
    return &colorRegistry{
        Red:   "red",
        Green: "green",
        Blue:  "blue",
    }
}

type colorRegistry struct {
    Red   string
    Green string
    Blue  string
}

func main() {
    fmt.Println(Colors.Red)
}

Suppose you also wanted some utility methods, like Colors.List(), and Colors.Parse("red"). And your colors were more complex and needed to be a struct. Then you might do something a bit like this:

package main

import (
    "errors"
    "fmt"
)

var Colors = newColorRegistry()

type Color struct {
    StringRepresentation string
    Hex                  string
}

func (c *Color) String() string {
    return c.StringRepresentation
}

func newColorRegistry() *colorRegistry {

    red := &Color{"red", "F00"}
    green := &Color{"green", "0F0"}
    blue := &Color{"blue", "00F"}

    return &colorRegistry{
        Red:    red,
        Green:  green,
        Blue:   blue,
        colors: []*Color{red, green, blue},
    }
}

type colorRegistry struct {
    Red   *Color
    Green *Color
    Blue  *Color

    colors []*Color
}

func (c *colorRegistry) List() []*Color {
    return c.colors
}

func (c *colorRegistry) Parse(s string) (*Color, error) {
    for _, color := range c.List() {
        if color.String() == s {
            return color, nil
        }
    }
    return nil, errors.New("couldn't find it")
}

func main() {
    fmt.Printf("%s\n", Colors.List())
}

At that point, sure it works, but you might not like how you have to repetitively define colors. If at this point you'd like to eliminate that, you could use tags on your struct and do some fancy reflecting to set it up, but hopefully this is enough to cover most people.