Demonstrate custom unmarshal

xml_test.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+	"encoding/xml"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type OutboundChannel struct {
+	ID string `xml:"id,attr"`
+}
+
+type Interface struct {
+	Name       string           `xml:"name,attr"`
+	OutChannel *OutboundChannel `xml:"-"`
+}
+
+type Root struct {
+	Interfaces []*Interface `xml:"interface"`
+}
+
+const example = `
+<root>
+	<interface name="et-0/0/0"></interface>
+	<outbound-channel id="1"></outbound-channel>
+	<interface name="et-0/0/1"></interface>
+	<interface name="et-0/0/2"></interface>
+	<outbound-channel id="3"></outbound-channel>
+</root>
+`
+
+func (r *Root) UnmarshalXML(d *xml.Decoder, _ xml.StartElement) error {
+	for {
+		tok, err := d.Token()
+		if err != nil {
+			return err
+		}
+
+		switch tok.(type) {
+		case xml.CharData:
+			continue // ignore whitespace
+		case xml.EndElement:
+			return nil
+		}
+
+		elem, ok := tok.(xml.StartElement)
+		if !ok {
+			return fmt.Errorf("invalid token encountered: %T", tok)
+		}
+		switch elem.Name.Local {
+		case "interface":
+			var v Interface
+			if err := d.DecodeElement(&v, &elem); err != nil {
+				return err
+			}
+			r.Interfaces = append(r.Interfaces, &v)
+		case "outbound-channel":
+			if len(r.Interfaces) == 0 {
+				// no interface encountered, skip this
+				continue
+			}
+
+			var v OutboundChannel
+			if err := d.DecodeElement(&v, &elem); err != nil {
+				return err
+			}
+
+			currentIf := r.Interfaces[len(r.Interfaces)-1]
+			currentIf.OutChannel = &v
+		}
+	}
+}
+
+func TestXMLUnmarshal(t *testing.T) {
+	var target Root
+	err := xml.Unmarshal([]byte(example), &target)
+	if err != nil {
+		t.Error(err)
+	}
+
+	require.Len(t, target.Interfaces, 3)
+	assert.Equal(t, "et-0/0/0", target.Interfaces[0].Name)
+	assert.Equal(t, "1", target.Interfaces[0].OutChannel.ID)
+
+	assert.Equal(t, "et-0/0/1", target.Interfaces[1].Name)
+	assert.Nil(t, target.Interfaces[1].OutChannel)
+
+	assert.Equal(t, "et-0/0/2", target.Interfaces[2].Name)
+	assert.Equal(t, "3", target.Interfaces[2].OutChannel.ID)
+}