Golang通过代码注释自动生成枚举类型插件库go-enum的使用

go-enum是一个用于Golang的枚举生成器，它可以通过代码注释自动生成枚举类型和相关功能代码。

工作原理

go-enum会处理带有特殊注释的类型声明，并生成包含iota定义和各种可选功能的代码。

基本示例

// ENUM(jpeg, jpg, png, tiff, gif)
type ImageType int

运行go-enum后会生成：

const (
    // ImageTypeJpeg is a ImageType of type Jpeg.
    ImageTypeJpeg ImageType = iota
    // ImageTypeJpg is a ImageType of type Jpg.
    ImageTypeJpg
    // ImageTypePng is a ImageType of type Png.
    ImageTypePng
    // ImageTypeTiff is a ImageType of type Tiff.
    ImageTypeTiff
    // ImageTypeGif is a ImageType of type Gif.
    ImageTypeGif
)

// String implements the Stringer interface.
func (x ImageType) String() string

// ParseImageType attempts to convert a string to a ImageType.
func ParseImageType(name string) (ImageType, error)

// MarshalText implements the text marshaller method.
func (x ImageType) MarshalText() ([]byte, error)

// UnmarshalText implements the text unmarshaller method.
func (x *ImageType) UnmarshalText(text []byte) error

字符串类型枚举

go-enum也支持字符串类型的枚举：

// ENUM(pending, running, completed, failed)
type StrState string

生成结果：

const (
    // StrStatePending is a StrState of type pending.
    StrStatePending StrState = "pending"
    // StrStateRunning is a StrState of type running.
    StrStateRunning StrState = "running"
    // StrStateCompleted is a StrState of type completed.
    StrStateCompleted StrState = "completed"
    // StrStateFailed is a StrState of type failed.
    StrStateFailed StrState = "failed"
)

完整示例

下面是一个更完整的示例，展示如何定义和使用go-enum：

// 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

生成的代码将包含：

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
)

// ...其他生成的函数...

安装和使用

安装

可以通过以下方式安装：

curl -fsSL "https://github.com/abice/go-enum/releases/download/$(GO_ENUM_VERSION)/go-enum_$(uname -s)_$(uname -m)" -o go-enum

或者使用Docker:

docker run -w /app -v $(pwd):/app abice/go-enum:$(GO_ENUM_VERSION)

在项目中使用

1. 在Go文件中添加生成指令：

//go:generate go-enum --marshal

1. 运行生成命令：

go generate ./...

Makefile示例

也可以在Makefile中使用：

STANDARD_ENUMS = ./example/animal_enum.go \
 ./example/color_enum.go

NULLABLE_ENUMS = ./example/sql_enum.go

$(STANDARD_ENUMS): GO_ENUM_FLAGS=--nocase --marshal --names --ptr
$(NULLABLE_ENUMS): GO_ENUM_FLAGS=--nocase --marshal --names --sqlnullint --ptr

enums: $(STANDARD_ENUMS) $(NULLABLE_ENUMS)

%_enum.go: %.go $(GOENUM) Makefile
 $(GOENUM) -f $*.go $(GO_ENUM_FLAGS)

命令选项

go-enum提供了多种选项来自定义生成行为：

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.
   --noprefix                      Prevents the constants generated from having the Enum as a prefix.
   --lower                         Adds lowercase variants of the enum strings for lookup.
   --nocase                        Adds case insensitive parsing to the enumeration.
   --marshal                       Adds text (and inherently json) marshalling functions.
   --sql                           Adds SQL database scan and value functions.
   --sqlint                        Tells the generator that a string typed enum should be stored in sql as an integer value.
   --flag                          Adds golang flag functions.
   --prefix value                  Adds a prefix with a user one.
   --names                         Generates a 'Names() []string' function.
   --values                        Generates a 'Values() []{{ENUM}}' function.
   --nocamel                       Removes the snake_case to CamelCase name changing.
   --ptr                           Adds a pointer method to get a pointer from const values.
   --sqlnullint                    Adds a Null{{ENUM}} type for marshalling a nullable int value to sql.
   --sqlnullstr                    Adds a Null{{ENUM}} type for marshalling a nullable string value to sql.
   --template value, -t value      Additional template file(s) to generate enums.
   --alias value, -a value         Adds or replaces aliases for a non alphanumeric value.
   --mustparse                     Adds a Must version of the Parse that will panic on failure.
   --forcelower                    Forces a camel cased comment to generate lowercased names.
   --forceupper                    Forces a camel cased comment to generate uppercased names.
   --nocomments                    Removes auto generated comments.
   --buildtag value, -b value      Adds build tags to a generated enum file.
   --help, -h                      show help
   --version, -v                   print the version

通过go-enum，你可以轻松地为Golang项目生成类型安全的枚举，并附带各种实用功能，如字符串转换、JSON序列化等。