Parse Error from Converting Json String to Struct - json

Question

i cannot parse the json value i am sending a playground link
Any idea about that? here is the link and codes
https://play.golang.org/p/qhZpS_-618s
package main
import (
"encoding/json"
"fmt"
//mapstructure "github.com/mitchellh/mapstructure"
)
type presence struct{
id string
m_type string
deny string
}
type jsonHandler struct {
name string
dat map[string]interface{}
}
func main() {
s := `["Presence",{"id":"905356870666#c.us","type":"unavailable","deny":true}]`
data := jsonHandler{}
json.Unmarshal([]byte(s), &data)
fmt.Printf("Operation: %s", data.name)
}
Output :
Operation:
Program exited.

Answer 1

Try with this one: https://play.golang.com/p/UICf_uNNFdC
I've commented a lot in order to enhance code readability. Be sure to handle error properly and remove debug print.
package main
import (
"encoding/json"
"log"
"strings"
)
type Presence struct {
Presence string
ID string `json:"id"`
Type string `json:"type"`
Deny bool `json:"deny"`
}
type JsonHandler struct {
Name string `json:"name"`
Dat Presence `json:"dat"`
}
func main() {
var (
// Used for unmarshal a given json
packedData []json.RawMessage
err error
// Data that does not have a related json key
name []byte
// Used for extract the raw data that will be unmarshalled into the Presence struct
temp []byte
// Nested json
jsonPresence Presence
handler JsonHandler
)
s := `["Presence",{"id":"905356870666#c.us","type":"unavailable","deny":true}]`
log.Println("Dealing with -> " + s)
// Unmarshall into a raw json message
err = json.Unmarshal([]byte(s), &packedData)
if err != nil {
panic(err)
}
// Extract the presence
log.Println("Presence: ", string(packedData[0]))
// Extract the nested json
log.Println("Packed: ", string(packedData[1]))
// NOTE: 0 refers to the first value of the JSON
name, err = packedData[0].MarshalJSON()
if err != nil {
panic(err)
}
log.Println("Value that does not have a key: " + string(name))
handler.Name = strings.Replace(string(name), "\"", "", -1)
// NOTE: 1 refers to the second value of the JSON, the entire JSON
// Unmarshal the nested Json into byte
temp, err = packedData[1].MarshalJSON()
if err != nil {
panic(err)
}
// Unmarshal the raw byte into the struct
err = json.Unmarshal(temp, &jsonPresence)
if err != nil {
panic(err)
}
log.Println("ID:", jsonPresence.ID)
log.Println("Type:", jsonPresence.Type)
log.Println("Deny:", jsonPresence.Deny)
handler.Dat = jsonPresence
log.Println("Data unmarshalled: ", handler)
}

Answer 2

Go Playground Link: https://play.golang.org/p/qe0jyFVNTH1
Few Problem are present in this:
1. Json Package can't refer the Unexported Structure Elements.So please use Deny instead of deny in the following snippet.This is applicable to all variables declared inside the structure
2. The json fields tag are incorrect. eg.mapstructure:"id" should be json:"id"
3. The json to be parsed contains two distinct elements i.e string "Presence" and nested json object.It can't be parsed as a single element.It is better to declare "Presence" as a key and nested json as the value.
4. The deny variable should be bool rather than string

Answer 3

Wow,solved problem by adding only these codes
Here Go Lang Link : https://play.golang.org/p/doHNWK58Cae
func (n *JsonHandler) UnmarshalJSON(buf []byte) error {
tmp := []interface{}{&n.Name, &n.Dat}
wantLen := len(tmp)
if err := json.Unmarshal(buf, &tmp); err != nil {
return err
}
if g, e := len(tmp), wantLen; g != e {
return fmt.Errorf("wrong number of fields in Notification: %d != %d", g, e)
}
return nil
}