go-enum

An enum generator for go

How it works

The goal of go-enum is to create an easy to use enum generator that will take a decorated type declaration like type EnumName int and create the associated constant values and funcs that will make life a little easier for adding new values. It's not perfect, but I think it's useful.

I took the output of the Stringer command as the String() method, and added a way to parse a string value.

Command options

go-enum --help
NAME:
   go-enum - An enum generator for go

USAGE:
   go-enum [global options] [arguments...]

GLOBAL OPTIONS:
   --file value, -f value  The file(s) to generate enums.  Use more than one flag for more files.
   --noprefix              Prevents the constants generated from having the Enum as a prefix. (default: false)
   --lower                 Adds lowercase variants of the enum strings for lookup. (default: false)
   --nocase                Adds case insensitive parsing to the enumeration (forces lower flag). (default: false)
   --marshal               Adds text (and inherently json) marshalling functions. (default: false)
   --sql                   Adds SQL database scan and value functions. (default: false)
   --flag                  Adds golang flag functions. (default: false)
   --prefix value          Replaces the prefix with a user one.
   --names                 Generates a 'Names() []string' function, and adds the possible enum values in the error response during parsing (default: false)
   --nocamel               Removes the snake_case to CamelCase name changing (default: false)
   --ptr                   Adds a pointer method to get a pointer from const values (default: false)
   --sqlnullint            Adds a Null{{ENUM}} type for marshalling a nullable int value to sql (default: false)
   --sqlnullstr            Adds a Null{{ENUM}} type for marshalling a nullable string value to sql.  If sqlnullint is specified too, it will be Null{{ENUM}}Str (default: false)
   --help, -h              show help (default: false)

Syntax

The parser looks for comments on your type defs and parse the enum declarations from it. The parser will look for ENUM( and continue to look for comma separated values until it finds a ). You can put values on the same line, or on multiple lines.
If you need to have a specific value jump in the enum, you can now specify that by adding =numericValue to the enum declaration. Keep in mind, this resets the data for all following values. So if you specify 50 in the middle of an enum, each value after that will be 51, 52, 53...

Comments

You can use comments inside enum that start with //
The comment must be at the end of the same line as the comment value, only then it will be added as a comment to the generated constant.

// Commented is an enumeration of commented values
/*
ENUM(
value1 // Commented value 1
value2
value3 // Commented value 3
)
*/
type Commented int

The generated comments in code will look something like:

...
const (
    // CommentedValue1 is a Commented of type Value1
    // Commented value 1
    CommentedValue1 Commented = iota
    // CommentedValue2 is a Commented of type Value2
    CommentedValue2
    // CommentedValue3 is a Commented of type Value3
    // Commented value 3
    CommentedValue3
)
...

Example

There are a few examples in the example directory. I've included one here for easy access, but can't guarantee it's up to date.

// Color is an enumeration of colors that are allowed.
/* ENUM(
Black, White, Red
Green = 33 // Green starts with 33
*/
// Blue
// grey=
// yellow
// blue-green
// red-orange
// yellow_green
// red-orange-blue
// )
type Color int32

The generated code will look something like:

// Code generated by go-enum
// DO NOT EDIT!

package example

import (
    "fmt"
    "strings"
)

const (
    // ColorBlack is a Color of type Black
    ColorBlack Color = iota
    // ColorWhite is a Color of type White
    ColorWhite
    // ColorRed is a Color of type Red
    ColorRed
    // ColorGreen is a Color of type Green
    // Green starts with 33
    ColorGreen Color = iota + 30
    // ColorBlue is a Color of type Blue
    ColorBlue
    // ColorGrey is a Color of type Grey
    ColorGrey
    // ColorYellow is a Color of type Yellow
    ColorYellow
    // ColorBlueGreen is a Color of type Blue-Green
    ColorBlueGreen
    // ColorRedOrange is a Color of type Red-Orange
    ColorRedOrange
    // ColorYellowGreen is a Color of type Yellow_green
    ColorYellowGreen
    // ColorRedOrangeBlue is a Color of type Red-Orange-Blue
    ColorRedOrangeBlue
)

const _ColorName = "BlackWhiteRedGreenBluegreyyellowblue-greenred-orangeyellow_greenred-orange-blue"

var _ColorMap = map[Color]string{
    0:  _ColorName[0:5],
    1:  _ColorName[5:10],
    2:  _ColorName[10:13],
    33: _ColorName[13:18],
    34: _ColorName[18:22],
    35: _ColorName[22:26],
    36: _ColorName[26:32],
    37: _ColorName[32:42],
    38: _ColorName[42:52],
    39: _ColorName[52:64],
    40: _ColorName[64:79],
}

// String implements the Stringer interface.
func (x Color) String() string {
    if str, ok := _ColorMap[x]; ok {
        return str
    }
    return fmt.Sprintf("Color(%d)", x)
}

var _ColorValue = map[string]Color{
    _ColorName[0:5]:                    0,
    strings.ToLower(_ColorName[0:5]):   0,
    _ColorName[5:10]:                   1,
    strings.ToLower(_ColorName[5:10]):  1,
    _ColorName[10:13]:                  2,
    strings.ToLower(_ColorName[10:13]): 2,
    _ColorName[13:18]:                  33,
    strings.ToLower(_ColorName[13:18]): 33,
    _ColorName[18:22]:                  34,
    strings.ToLower(_ColorName[18:22]): 34,
    _ColorName[22:26]:                  35,
    strings.ToLower(_ColorName[22:26]): 35,
    _ColorName[26:32]:                  36,
    strings.ToLower(_ColorName[26:32]): 36,
    _ColorName[32:42]:                  37,
    strings.ToLower(_ColorName[32:42]): 37,
    _ColorName[42:52]:                  38,
    strings.ToLower(_ColorName[42:52]): 38,
    _ColorName[52:64]:                  39,
    strings.ToLower(_ColorName[52:64]): 39,
    _ColorName[64:79]:                  40,
    strings.ToLower(_ColorName[64:79]): 40,
}

// ParseColor attempts to convert a string to a Color
func ParseColor(name string) (Color, error) {
    if x, ok := _ColorValue[name]; ok {
        return x, nil
    }
    return Color(0), fmt.Errorf("%s is not a valid Color", name)
}

// MarshalText implements the text marshaller method
func (x Color) MarshalText() ([]byte, error) {
    return []byte(x.String()), nil
}

// UnmarshalText implements the text unmarshaller method
func (x *Color) UnmarshalText(text []byte) error {
    name := string(text)
    tmp, err := ParseColor(name)
    if err != nil {
        return err
    }
    *x = tmp
    return nil
}

Adding it to your project

1. go get github.com/abice/go-enum
2. Add a go:generate line to your file like so... //go:generate go-enum -f=$GOFILE --marshal
3. Run go generate like so go generate ./...
4. Enjoy your newly created Enumeration