ANisus ANisus - 1 month ago 15
JSON Question

Partly JSON unmarshal into a map in Go

My websocket server will receive and unmarshal JSON data. This data will always be wrapped in an object with key/value pairs. The key-string will act as value identifier, telling the Go server what kind of value it is. By knowing what type of value, I can then proceed to JSON unmarshal the value into the correct type of struct.

Each json-object might contain multiple key/value pairs.

Example JSON:

{
"sendMsg":{"user":"ANisus","msg":"Trying to send a message"},
"say":"Hello"
}


Is there any easy way using the
"encoding/json"
package to do this?

package main

import (
"encoding/json"
"fmt"
)

// the struct for the value of a "sendMsg"-command
type sendMsg struct {
user string
msg string
}
// The type for the value of a "say"-command
type say string

func main(){
data := []byte(`{"sendMsg":{"user":"ANisus","msg":"Trying to send a message"},"say":"Hello"}`)

// This won't work because json.MapObject([]byte) doesn't exist
objmap, err := json.MapObject(data)

// This is what I wish the objmap to contain
//var objmap = map[string][]byte {
// "sendMsg": []byte(`{"user":"ANisus","msg":"Trying to send a message"}`),
// "say": []byte(`"hello"`),
//}
fmt.Printf("%v", objmap)
}


Thanks for any kind of suggestion/help!

Answer

This can be accomplished by Unmarshalling into a map[string]json.RawMessage.

var objmap map[string]*json.RawMessage
err := json.Unmarshal(data, &objmap)

To further parse sendMsg, you could then do something like:

var s sendMsg
err = json.Unmarshal(*objmap["sendMsg"], &s)

For say, you can do the same thing and unmarshal into a string:

var str string
err = json.Unmarshal(*objmap["say"], &str)