add utility to use in app (#290)

string.go

@@ -68,6 +68,17 @@ func (ss StringSet) Remove(value string) {
 	delete(ss, value)
 }
 
+// ToList converts the set into a list of strings.
+func (ss StringSet) ToList() []string {
+	list := make([]string, len(ss))
+	i := 0
+	for key := range ss {
+		list[i] = key
+		i++
+	}
+	return list
+}
+
 // StringSliceRemove removes an element from the slice at the given position.
 func StringSliceRemove(from []string, at int) []string {
 	if at >= len(from) {

string_test.go

@@ -44,6 +44,16 @@ func TestStringSet(t *testing.T) {
 	ss.Remove("no-op")
 	_, ok = ss["foo"]
 	test.That(t, ok, test.ShouldBeTrue)
+
+	ss.Remove("foo")
+	test.That(t, len(ss), test.ShouldEqual, 0)
+
+	ss.Add("hello")
+	ss.Add("bye")
+
+	listView := ss.ToList()
+	test.That(t, len(listView), test.ShouldEqual, 2)
+	test.That(t, listView, test.ShouldResemble, []string{"hello", "bye"})
 }
 
 func TestStringSliceRemove(t *testing.T) {