Cobra允许您通过pflag.(*FlagSet).Var()方法（来自Cobra使用的https://github.com/spf13/pflag包）定义自定义值类型用作标志。您必须创建一个实现pflag.Value接口的新类型：

type Value interface {
    String() string
    Set(string) error
    Type() string
}

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示例类型定义：

type myEnum string
const (
    myEnumFoo myEnum = "foo"
    myEnumBar myEnum = "bar"
    myEnumMoo myEnum = "moo"
)
// String is used both by fmt.Print and by Cobra in help text
func (e *myEnum) String() string {
    return string(*e)
}
// Set must have pointer receiver so it doesn't change the value of a copy
func (e *myEnum) Set(v string) error {
    switch v {
    case "foo", "bar", "moo":
        *e = myEnum(v)
        return nil
    default:
        return errors.New(`must be one of "foo", "bar", or "moo"`)
    }
}
// Type is only used in help text
func (e *myEnum) Type() string {
    return "myEnum"
}

型
注册示例：

func init() {
    var flagMyEnum = myEnumFoo
    var myCmd = &cobra.Command{
        Use:   "mycmd",
        Short: "A brief description of your command",
        Run: func(cmd *cobra.Command, args []string) {
            fmt.Println("myenum value:", flagMyEnum)
        },
    }
    rootCmd.AddCommand(myCmd)
    myCmd.Flags().Var(&flagMyEnum, "myenum", `my custom enum. allowed: "foo", "bar", "moo"`)
}

型
示例用法：（注意下面控制台输出中的第一行）

$ go run . mycmd --myenum raz
Error: invalid argument "raz" for "--myenum" flag: must be one of "foo", "bar", or "moo"
Usage:
  main mycmd [flags]
Flags:
  -h, --help            help for mycmd
      --myenum myEnum   my custom enum. allowed: "foo", "bar", "moo" (default foo)
exit status 1

$ go run . mycmd --myenum bar
myenum value: bar

完成

要添加自动补全功能，可以使用隐藏的文档cobra/shell_completions. md #completions-for-flags。对于我们的示例，您可以添加如下内容：

func init() {
    // ...
    myCmd.Flags().Var(&flagMyEnum, "myenum", `my custom enum. allowed: "foo", "bar", "moo"`)
    myCmd.RegisterFlagCompletionFunc("myenum", myEnumCompletion)
}
// myEnumCompletion should probably live next to the myEnum definition
func myEnumCompletion(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
    return []string{
        "foo\thelp text for foo",
        "bar\thelp text for bar",
        "moo\thelp text for moo",
    }, cobra.ShellCompDirectiveDefault
}

型
示例用法：

$ go build -o main .
$ source <(main completion bash)
$ main mycmd --myenum <TAB><TAB>
bar  (help text for bar)
foo  (help text for foo)
moo  (help text for moo)

型

它看起来像一个enumflag包作为一个附加组件发布，以满足此用例：https://pkg.go.dev/github.com/thediveo/enumflag

package main
import (
    "fmt"
    "github.com/spf13/cobra"
    "github.com/thediveo/enumflag"
)
// ① Define your new enum flag type. It can be derived from enumflag.Flag, but
// it doesn't need to be as long as it is compatible with enumflag.Flag, so
// either an int or uint.
type FooMode enumflag.Flag
// ② Define the enumeration values for FooMode.
const (
    Foo FooMode = iota
    Bar
)
// ③ Map enumeration values to their textual representations (value
// identifiers).
var FooModeIds = map[FooMode][]string{
    Foo: {"foo"},
    Bar: {"bar"},
}
// User-defined enum flag types should be derived from "enumflag.Flag"; however
// this is not strictly necessary as long as they can be converted into the
// "enumflag.Flag" type. Actually, "enumflag.Flag" is just a fancy name for an
// "uint". In order to use such user-defined enum flags, simply wrap them using
// enumflag.New.
func main() {
    // ④ Define your enum flag value.
    var foomode FooMode
    rootCmd := &cobra.Command{
        Run: func(cmd *cobra.Command, _ []string) {
            fmt.Printf("mode is: %d=%q\n",
                foomode,
                cmd.PersistentFlags().Lookup("mode").Value.String())
        },
    }
    // ⑤ Define the CLI flag parameters for your wrapped enum flag.
    rootCmd.PersistentFlags().VarP(
        enumflag.New(&foomode, "mode", FooModeIds, enumflag.EnumCaseInsensitive),
        "mode", "m",
        "foos the output; can be 'foo' or 'bar'")
    rootCmd.SetArgs([]string{"--mode", "bAr"})
    _ = rootCmd.Execute()
}

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注意：它似乎不包括完成逻辑。

虽然很难证明一个否定的，它不看这是目前的一个功能。