4 files changed, 73 insertions, 0 deletions

diff --git a/flag.go b/flag.go
index 9beeda8..60c2038 100644
--- a/flag.go
+++ b/flag.go
@@ -190,6 +190,12 @@ type Value interface {
 	Type() string
 }
 
+type SliceValue interface {
+	Append(string) error
+	Replace([]string) error
+	GetSlice() []string
+}
+
 // sortFlags returns the flags as a slice in lexicographical sorted order.
 func sortFlags(flags map[NormalizedName]*Flag) []*Flag {
 	list := make(sort.StringSlice, len(flags))
diff --git a/int_slice.go b/int_slice.go
index 1e7c9ed..e71c39d 100644
--- a/int_slice.go
+++ b/int_slice.go
@@ -51,6 +51,36 @@ func (s *intSliceValue) String() string {
 	return "[" + strings.Join(out, ",") + "]"
 }
 
+func (s *intSliceValue) Append(val string) error {
+	i, err := strconv.Atoi(val)
+	if err != nil {
+		return err
+	}
+	*s.value = append(*s.value, i)
+	return nil
+}
+
+func (s *intSliceValue) Replace(val []string) error {
+	out := make([]int, len(val))
+	for i, d := range val {
+		var err error
+		out[i], err = strconv.Atoi(d)
+		if err != nil {
+			return err
+		}
+	}
+	*s.value = out
+	return nil
+}
+
+func (s *intSliceValue) GetSlice() []string {
+	out := make([]string, len(*s.value))
+	for i, d := range *s.value {
+		out[i] = strconv.Itoa(d)
+	}
+	return out
+}
+
 func intSliceConv(val string) (interface{}, error) {
 	val = strings.Trim(val, "[]")
 	// Empty string would cause a slice with one (empty) entry
diff --git a/string_slice.go b/string_slice.go
index 0cd3ccc..74b934b 100644
--- a/string_slice.go
+++ b/string_slice.go
@@ -62,6 +62,20 @@ func (s *stringSliceValue) String() string {
 	return "[" + str + "]"
 }
 
+func (s *stringSliceValue) Append(val string) error {
+	*s.value = append(*s.value, val)
+	return nil
+}
+
+func (s *stringSliceValue) Replace(val []string) error {
+	*s.value = val
+	return nil
+}
+
+func (s *stringSliceValue) GetSlice() []string {
+	return  *s.value
+}
+
 func stringSliceConv(sval string) (interface{}, error) {
 	sval = sval[1 : len(sval)-1]
 	// An empty string would cause a slice with one (empty) string
diff --git a/string_slice_test.go b/string_slice_test.go
index c41f3bd..9a7e246 100644
--- a/string_slice_test.go
+++ b/string_slice_test.go
@@ -251,3 +251,26 @@ func TestSSWithSquareBrackets(t *testing.T) {
 		}
 	}
 }
+
+func TestSSAsSliceValue(t *testing.T) {
+	var ss []string
+	f := setUpSSFlagSet(&ss)
+
+	in := []string{"one", "two"}
+	argfmt := "--ss=%s"
+	arg1 := fmt.Sprintf(argfmt, in[0])
+	arg2 := fmt.Sprintf(argfmt, in[1])
+	err := f.Parse([]string{arg1, arg2})
+	if err != nil {
+		t.Fatal("expected no error; got", err)
+	}
+
+	f.VisitAll(func(f *Flag) {
+		if val, ok := f.Value.(SliceValue); ok {
+			_ = val.Replace([]string{"three"})
+		}
+	})
+	if len(ss) != 1 || ss[0]!= "three" {
+		t.Fatalf("Expected ss to be overwritten with 'three', but got: %s", ss)
+	}
+}
\ No newline at end of file