Using the xml
package in golang I'm having trouble unmarshalling a list of non-homogenous types. Consider the following XML document whose nested elements are a list of non-homogenous types:
<mydoc>
<foo>Foo</foo>
<bar>Bar</bar>
<foo>Another Foo</foo>
<foo>Foo #3</foo>
<bar>Bar 2</bar>
</mydoc>
And the following golang code to test XML un/marshalling (also here on the go playground):
package main
import "encoding/xml"
import "fmt"
const sampleXml = `
<mydoc>
<foo>Foo</foo>
<bar>Bar</bar>
<foo>Another Foo</foo>
<foo>Foo #3</foo>
<bar>Bar 2</bar>
</mydoc>
`
type MyDoc struct {
XMLName xml.Name `xml:"mydoc"`
Items []Item
}
type Item interface {
IsItem()
}
type Foo struct {
XMLName xml.Name `xml:"foo"`
Name string `xml:",chardata"`
}
func (f Foo) IsItem() {}
type Bar struct {
XMLName xml.Name `xml:"bar"`
Nombre string `xml:",chardata"`
}
func (b Bar) IsItem() {}
func main() {
doMarshal()
doUnmarshal()
}
func doMarshal() {
myDoc := MyDoc{
Items: []Item{
Foo{Name: "Foo"},
Bar{Nombre: "Bar"},
Foo{Name: "Another Foo"},
Foo{Name: "Foo #3"},
Bar{Nombre: "Bar 2"},
},
}
bytes, err := xml.MarshalIndent(myDoc, "", " ")
if err != nil {
panic(err)
}
// Prints an XML document just like "sampleXml" above.
println(string(bytes))
}
func doUnmarshal() {
myDoc := MyDoc{}
err := xml.Unmarshal([]byte(sampleXml), &myDoc)
if err != nil {
panic(err)
}
// Fails to unmarshal the "Item" elements into their respective structs.
fmt.Printf("ERR: %#v", myDoc)
}
You'll see that doMarshal()
produces the exact XML document I expect; however, doUnmarshal()
fails to deserialize the "Item" elements into their respective structs. I've tried a few changes but nothing seems to get them to unmarshal properly (creating storage for myDoc.Items
, changing the type of "Items" to []*Item
[and others], fiddling with the XML tags, etc).
Any ideas how to get xml.Unmarshal(...)
to deserialize a list of elements of unrelated types?