Handy code to implement string map for pflag

flag.Value

package app

import (
	"fmt"
	"strings"
)

// See: https://github.com/spf13/pflag/issues/129
// $ mycommand --string-map-option "a=b,c=d"

type StringMap struct {
	Values []map[string][]string
}

// Implement the flag.Value interface

func (s *StringMap) Set(value string) error {

	allValues := strings.Split(value, ",")
	stringMap := make(map[string][]string, len(allValues))

	for _, arg := range strings.Split(value, ",") {
		x := strings.Split(arg, "=")
		if len(x) < 2 {
			if arg == "" {
				arg = "empty"
			}
			return fmt.Errorf("Incorrect key=value format for %s", arg)
		}
		stringMap[x[0]] = append(stringMap[x[0]], x[1])
	}
	s.Values = append(s.Values, stringMap)

	return nil
}

func (s *StringMap) String() string {
	return fmt.Sprintf("%v", *s)
}

func (s *StringMap) Type() string {
	return fmt.Sprintf("%T", s)
}

func (s *StringMap) Usage() string {
	return "\"a=1,a=2,a=3,b=4,c=5\" returns map[string{key}][]string{values} "
}