Go-genenum

This is a tool to generate enums and common optimized helpers for them.

Installation

go install github.com/saturn4er/go-genenum/cmd/go-genenum

Basic usage

Create a file with enums declaration in yaml format. For example, enums.yaml:

- name: A
  values: [ "Value1", "Value2", "Value3" ]

then run go-genenum enums.yaml -o enums.go -p my_package and it will generate enums.go

package my_package

type A byte

const (
	AValue1 A = iota + 1
	AValue2
	AValue3
)

Helpers

Usually, you need some additional methods for enums, like String(), IsValid(), IsValue1(), or create some group of enum values, so you can easily check if this value belongs to some group. But you don't want to support it, as it's really easy to forget to add some handler for new value.

go-genenum can generate these methods for you. Just add helpers section to your yaml file:

String

String helper will generate optimized String() method for your enum.

- name: A
  values: [ "Value1", "Value2", "Value3" ]
  helpers:
    string: true

generates:

func (a A) String() string {
	if a < 1 || a > 3 {
		return "A(" + strconv.FormatInt(int64(a), 10) + ")"
	}
	const names = "Value1Value2Value3"

	var indexes = [...]int32{0, 6, 12, 18}

	return names[indexes[a-1]:indexes[a]]
}

IsValid

IsValid helper will generate IsValid() method, which will check if value is valid for this enum.

- name: A
  values: [ "Value1", "Value2", "Value3" ]
  helpers:
    is_valid: true

generates:

func (a A) IsValid() bool {
	return a > 0 && a < 4
}

Validate

Validate helper will generate Validate() method, which will check if value is valid for this enum and return error if not.

- name: A
  values: [ "Value1", "Value2", "Value3" ]
  helpers:
    validate: true

generates:

type InvalidAValueError byte

func (e InvalidAValueError) Error() string {
	return fmt.Sprintf("invalid A(%d)", e)
}
func (a A) Validate() error {
	if a < 1 || a > 4 {
		return InvalidAValueError(a)
	}
	return nil
}

Is

Is helper will generate methods for each value, which will check if value is equal to this value.

- name: A
  values: [ "Value1", "Value2", "Value3" ]
  helpers:
    is: true

generates:

func (a A) IsValue1() bool {
	return a == AValue1
}
func (a A) IsValue2() bool {
	return a == AValue2
}
func (a A) IsValue3() bool {
	return a == AValue3
}

Categories

Categories helper will generate methods for each category, which will check if value belongs to this category.

- name: A
  values: [ "Value1", "Value2", "Value3" ]
  helpers:
    categories:
      - name: "First"
        values: [ "Value1", "Value2" ]
      - name: "Second"
        values: [ "Value3" ]

generates:

var FirstAS = []A{
	AValue1,
	AValue2,
}

func (a A) IsFirst() bool {
	if a < 1 || a > 4 {
		return false
	}
	return []bool{false, true, true, false}[a]
}

var SecondAS = []A{
	AValue3,
}

func (a A) IsSecond() bool {
	if a < 1 || a > 4 {
		return false
	}
	return []bool{false, false, false, true}[a]
}