code review 842041: Flags: add user-defined flag types. The change is reall...

Flags: add user-defined flag types. The change is really no code; it's just publishing
the set() method and add() functions.  But we rename add() to Var() for consistency.
Also rename FlagValue to Value for simplicity.

Also, delete the check for multiple settings for a flag.  This makes it possible to
define a flag that collects values, such as into a slice of strings.

type flagVar []string

func (f *flagVar) String() string {
	return fmt.Sprint(v)
}

func (f *flagVar) Set(value string) bool {
	if v == nil {
		v = make(flagVar, 1)
	} else {
		nv := make(flagVar, len(v)+1)
		copy(nv, v)
		v = nv
	}
	v[len(v)-1] = value
	return true
}

var v flagVar

func main() {
	flag.Var(&v, "testV", "multiple values build []string")
	flag.Parse()
	fmt.Printf("v = %v\n", v)
}

[r, 2010-03-30 00:01:21]

Hello golang-dev@googlegroups.com,

I'd like you to review this change.

[rsc1, 2010-03-30 00:06:14]

LGTM

[r, 2010-03-30 00:37:25]

*** Submitted as http://code.google.com/p/go/source/detail?r=6070517caba0 ***

Flags: add user-defined flag types. The change is really no code; it's just
publishing
the set() method and add() functions.  But we rename add() to Var() for
consistency.
Also rename FlagValue to Value for simplicity.

Also, delete the check for multiple settings for a flag.  This makes it possible
to
define a flag that collects values, such as into a slice of strings.

type flagVar []string

func (f *flagVar) String() string {
	return fmt.Sprint(v)
}

func (f *flagVar) Set(value string) bool {
	if v == nil {
		v = make(flagVar, 1)
	} else {
		nv := make(flagVar, len(v)+1)
		copy(nv, v)
		v = nv
	}
	v[len(v)-1] = value
	return true
}

var v flagVar

func main() {
	flag.Var(&v, "testV", "multiple values build []string")
	flag.Parse()
	fmt.Printf("v = %v\n", v)
}

R=rsc
CC=golang-dev
http://codereview.appspot.com/842041