Parse XML tag to boolean if it exists when unmarshalling

Question

I'm trying to parse XML tag into a boolean if it exists. The tags inside <status> can be <active />, <available /> or <invalid /> and only one of these tag exists inside <status>.

Here's my current attempt:

package main

import (
    "encoding/xml"
    "fmt"
)

type Response struct {
    XMLName      xml.Name `xml:"domain"`
    Authority    string   `xml:"authority,attr"`
    RegistryType string   `xml:"registryType,attr"`
    EntityClass  string   `xml:"entityClass,attr"`
    EntityName   string   `xml:"entityName,attr"`
    DomainName   string   `xml:"domainName"`
    Status       Status   `xml:"status"`
}

type Status struct {
    Active    bool `xml:"active,omitempty"`
    Available bool `xml:"available,omitempty"`
    Invalid   bool `xml:"invalid,omitempty"`
}

func main() {

    str := `
<domain authority="domain.fi" registryType="dchk1" entityClass="domain-name" entityName="esimerkki.fi">
  <domainName>esimerkki.fi</domainName>
  <status>
    <active />
  </status>
</domain>
`

    var ans Response
    err := xml.Unmarshal([]byte(str), &ans)
    if err != nil {
        panic(err)
    }

    fmt.Printf(`%#v`, ans.Status)
}

This returns all Status.* as false and not Status.Active = true as expected. How can you get the expected result?

Second attempt with pointers:

type Status struct {
    Active    *bool `xml:"active,omitempty"`
    Available *bool `xml:"available,omitempty"`
    Invalid   *bool `xml:"invalid,omitempty"`
}

*ans.Status.Active still false.

Answer 1

As @mh-cbon suggested simply checking for if pointer wasn't nil for *bool was enough to determine if that tag existed. But I went and turned the XML response struct into proper Response struct which only contains needed information and Status into a constant.

So now it's:

// Raw XML DTO
type XmlResponse struct {
    XMLName      xml.Name  `xml:"domain"`
    Authority    string    `xml:"authority,attr"`
    RegistryType string    `xml:"registryType,attr"`
    EntityClass  string    `xml:"entityClass,attr"`
    EntityName   string    `xml:"entityName,attr"`
    DomainName   string    `xml:"domainName"`
    Status       XmlStatus `xml:"status"`
}

// Raw XML DTO
type XmlStatus struct {
    Active    *bool `xml:"active,omitempty"`
    Available *bool `xml:"available,omitempty"`
    Invalid   *bool `xml:"invalid,omitempty"`
}

// Return Response struct which doesn't have the unnecessary XML
func (x XmlResponse) GetResponse() Response {
    st := Invalid // Default to invalid

    if x.Status.Active != nil {
        st = Active
    } else if x.Status.Available != nil {
        st = Available
    } else if x.Status.Invalid != nil {
        st = Invalid
    }

    return Response{
        Domain: x.DomainName,
        Status: st,
    }
}

// Proper response parsed from XML
type Response struct {
    Domain string
    Status Status
}

type Status uint8

const (
    Invalid Status = iota
    Active
    Available
)

And parsing happens as:

var xmlresp XmlResponse
err := xml.Unmarshal([]byte(str), &xmlresp)
if err != nil {
    panic(err)
}

ans := xmlresp.GetResponse()

fmt.Printf(`%#v`, ans)