Implement UnmarshalYAML

cronexpr.go

@@ -44,6 +44,10 @@ type Expression struct {
 	yearList               []int
 }
 
+func (expr Expression) String() string {
+	return fmt.Sprintf("(%s)", expr.expression)
+}
+
 /******************************************************************************/
 
 // MustParse returns a new Expression pointer. It expects a well-formed cron
@@ -85,6 +89,7 @@ func Parse(cronLine string) (*Expression, error) {
 	var field = 0
 	var err error
 
+	expr.expression = cronLine
 	// second field (optional)
 	if fieldCount == 7 {
 		err = expr.secondFieldHandler(cron[indices[field][0]:indices[field][1]])
@@ -144,6 +149,20 @@ func Parse(cronLine string) (*Expression, error) {
 	return &expr, nil
 }
 
+func (expr *Expression) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var cronLine string
+	if err := unmarshal(&cronLine); err != nil {
+		return err
+	}
+	var err error
+	expression, err := Parse(cronLine)
+	if err != nil {
+		return err
+	}
+	*expr = *expression
+	return nil
+}
+
 /******************************************************************************/
 
 // Next returns the closest time instant immediately following `fromTime` which

cronexpr_test.go

@@ -17,6 +17,8 @@ package cronexpr
 import (
 	"testing"
 	"time"
+
+	yaml "gopkg.in/yaml.v2"
 )
 
 /******************************************************************************/
@@ -236,6 +238,28 @@ func TestZero(t *testing.T) {
 
 /******************************************************************************/
 
+type Config struct {
+	Expression Expression `yaml:"Expression"`
+}
+
+func TestUnmarshaler(t *testing.T) {
+	var config Config
+	err := yaml.Unmarshal([]byte(`Expression: "* * * * *"`), &config)
+	if err != nil {
+		t.Errorf("Unexpected error while unmarshaling")
+	}
+	if config.Expression.String() != "(* * * * *)" {
+		t.Errorf("Unexpected value when unmarshaled")
+	}
+
+	err = yaml.Unmarshal([]byte(`Expression: * * * * *`), &config)
+	if err == nil {
+		t.Errorf("Expected an error")
+	}
+}
+
+/******************************************************************************/
+
 func TestNextN(t *testing.T) {
 	expected := []string{
 		"Sat, 30 Nov 2013 00:00:00",