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
Options:

  -h, --help       display help information
  -f, --file      *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.
      --lower      Adds lowercase variants of the enum strings for lookup.
      --marshal    Adds text marshalling functions.
	  --json       Adds json marshalling functions.
      --sql        Adds SQL database scan and value functions.
      --flag       Adds golang flag functions.
      --prefix     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

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
// )
type Color int32

The generated code will look something like:

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
)

const _ColorName = "BlackWhiteRedGreenBluegreyyellowblue-greenred-orange"

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],
}

func (i Color) String() string {
	if str, ok := _ColorMap[i]; ok {
		return str
	}
	return fmt.Sprintf("Color(%d)", i)
}

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,
}

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

func (x *Color) MarshalText() ([]byte, error) {
	return []byte(x.String()), nil
}

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