Merge pull request #30 from alexflint/scalar_pointers

add support for pointers and TextUnmarshaler

1 files changed, 23 insertions, 8 deletions

diff --git a/scalar.go b/scalar.go
index a3bafe4..67b4540 100644
--- a/scalar.go
+++ b/scalar.go
@@ -8,19 +8,33 @@ import (
 	"time"
 )
 
-var (
-	durationType        = reflect.TypeOf(time.Duration(0))
-	textUnmarshalerType = reflect.TypeOf([]encoding.TextUnmarshaler{}).Elem()
-)
-
 // set a value from a string
 func setScalar(v reflect.Value, s string) error {
 	if !v.CanSet() {
 		return fmt.Errorf("field is not exported")
 	}
 
-	// If we have a time.Duration then use time.ParseDuration
-	if v.Type() == durationType {
+	// If we have a nil pointer then allocate a new object
+	if v.Kind() == reflect.Ptr && v.IsNil() {
+		v.Set(reflect.New(v.Type().Elem()))
+	}
+
+	// Get the object as an interface
+	scalar := v.Interface()
+
+	// If it implements encoding.TextUnmarshaler then use that
+	if scalar, ok := scalar.(encoding.TextUnmarshaler); ok {
+		return scalar.UnmarshalText([]byte(s))
+	}
+
+	// If we have a pointer then dereference it
+	if v.Kind() == reflect.Ptr {
+		v = v.Elem()
+	}
+
+	// Switch on concrete type
+	switch scalar.(type) {
+	case time.Duration:
 		x, err := time.ParseDuration(s)
 		if err != nil {
 			return err
@@ -29,6 +43,7 @@ func setScalar(v reflect.Value, s string) error {
 		return nil
 	}
 
+	// Switch on kind so that we can handle derived types
 	switch v.Kind() {
 	case reflect.String:
 		v.SetString(s)
@@ -57,7 +72,7 @@ func setScalar(v reflect.Value, s string) error {
 		}
 		v.SetFloat(x)
 	default:
-		return fmt.Errorf("not a scalar type: %s", v.Kind())
+		return fmt.Errorf("cannot parse argument into %s", v.Type().String())
 	}
 	return nil
 }