in progress

json/map.go

@@ -160,13 +160,31 @@ func (s Map) String(key, defaultVal string) string {
 	return defaultVal
 }
 
-func (s Map) Bytes(key, defaultVal []byte) []byte {
+func (s Map) StringWithError(key, defaultVal string) (string, error) {
+	if iface, check := s[key]; check {
+		val := val(iface, defaultVal).String()
+		if val == defaultVal {
+			return defaultVal, fmt.Errorf("FIELD [%s] IS EMPTY", key)
+		}
+		return val, nil
+	}
+	return defaultVal, fmt.Errorf("FIELD [%s] IS NOT EXISTS", key)
+}
+
+func (s Map) Bytes(key string, defaultVal []byte) []byte {
 	if iface, check := s[key]; check {
 		return []byte(val(iface, defaultVal).String())
 	}
 	return defaultVal
 }
 
+func (s Map) BytesWithError(key string, defaultVal []byte) ([]byte, error) {
+	if iface, check := s[key]; check {
+		return []byte(val(iface, defaultVal).String()), nil
+	}
+	return defaultVal, fmt.Errorf("FIELD [%s] IS NOT EXISTS", key)
+}
+
 func (s Map) StringVal(key, defaultVal string) string {
 	if iface, check := s[key]; check {
 		return fmt.Sprint(iface)