Unmarshalling XML with (xpath)conditions - xml-parsing

Question

I'm trying to unmarshall some XML which is structured like the following example:
<player>
<stat type="first_name">Somebody</stat>
<stat type="last_name">Something</stat>
<stat type="birthday">06-12-1987</stat>
</player>
It's dead easy to unmarshal this into a struct like
type Player struct {
Stats []Stat `xml:"stat"`
}
but I'm looking to find a way to unmarshal it into a struct that's more like
type Player struct {
FirstName string `xml:"stat[#Type='first_name']"`
LastName string `xml:"stat[#Type='last_name']"`
Birthday Time `xml:"stat[#Type='birthday']"`
}
is there any way to do this with the standard encoding/xml package?
If not, can you give me a hint how one would split down such a "problem" in go? (best practices on go software architecture for such a task, basically).
thank you!

Answer 1

The encoding/xml package doesn't implement xpath, but does have a simple set of selection methods it can use.
Here's an example of how you could unmarshal the XML you have using encoding/xml. Because the stats are all of the same type, with the same attributes, the easiest way to decode them will be into a slice of the same type. http://play.golang.org/p/My10GFiWDa
var doc = []byte(`<player>
<stat type="first_name">Somebody</stat>
<stat type="last_name">Something</stat>
<stat type="birthday">06-12-1987</stat>
</player>`)
type Player struct {
XMLName xml.Name `xml:"player"`
Stats []PlayerStat `xml:"stat"`
}
type PlayerStat struct {
Type string `xml:"type,attr"`
Value string `xml:",chardata"`
}
And if it's something you need to transform often, you could do the transformation by using an UnamrshalXML method: http://play.golang.org/p/htoOSa81Cn
type Player struct {
XMLName xml.Name `xml:"player"`
FirstName string
LastName string
Birthday string
}
func (p *Player) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
for {
t, err := d.Token()
if err == io.EOF {
break
} else if err != nil {
return err
}
if se, ok := t.(xml.StartElement); ok {
t, err = d.Token()
if err != nil {
return err
}
var val string
if c, ok := t.(xml.CharData); ok {
val = string(c)
} else {
// not char data, skip for now
continue
}
// assuming we have exactly one Attr
switch se.Attr[0].Value {
case "first_name":
p.FirstName = val
case "last_name":
p.LastName = val
case "birthday":
p.Birthday = val
}
}
}
return nil
}