How to Partially Unmarshal JSON into a Go Map?

Unmarshalling Partial JSON into a Map in Go

Partially unmarshalling JSON data into a map can be useful when the JSON is structured in a specific way, with a key-value structure where the key identifies the type of value. This approach enables efficient processing and type-specific handling of the data.

Consider the following JSON example:

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

To parse this JSON using the "encoding/json" package, you can unmarshal it into a map of strings to JSON "RawMessage" objects:

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

// Accessing the "sendMsg" value:
var s sendMsg
err = json.Unmarshal(objmap["sendMsg"], &s)

// Accessing the "say" value:
var str string
err = json.Unmarshal(objmap["say"], &str)

To unmarshal into specific data types, you need to export the struct fields in your sendMsg struct:

type sendMsg struct {
    User string
    Msg  string
}

This approach provides flexibility in handling JSON data with varying structures and allows for type-safe unmarshalling based on the key in the JSON object.

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