How to Unmarshal JSON with Unknown Field Names into a Go Struct?

Unmarshaling JSON with Unknown Fieldnames to a Struct

This scenario arises when the JSON response contains fields with unknown or dynamic names. To address this, we can utilize a combination of a map and a struct to capture the data.

Modified Code:

package main

import "fmt"
import "encoding/json"

var body = []byte(`{
    "unknown_field": {
            "known_field_1": [[1,2,3,4,5],[10,20,30,40,50],[100,200,300,400,500]],
            "known_field_2": [[11,21,31,41,51]],
            "known_field_3": [[12,22,32,42,52],[14,44,34,44,54]]
        }
}`)

type mData struct {
    KnownField1 [][5]int `json:"known_field_1"`
    KnownField2 [][5]int `json:"known_field_2"`
    KnownField3 [][5]int `json:"known_field_3"`
}

var data map[string]mData

func main() {
    if err := json.Unmarshal(body, &data); err != nil {
        panic(err)
    }

    fmt.Println(data)
    for k, v := range data {
        fmt.Println(k, v)
    }
}

Explanation:

• We define a mData struct to represent the known fields in the JSON.
• We create a map data, where the keys are the unknown fieldnames and the values are instances of mData.
• During unmarshalling, json.Unmarshal assigns the JSON data to the corresponding fields in mData based on the field names.
• The keys of the data map are the dynamic fieldnames from the JSON.

Output:

map[unknown_field:{[[1 2 3 4 5] [10 20 30 40 50] [100 200 300 400 500]] [[11 21 31 41 51]] [[12 22 32 42 52] [14 44 34 44 54]]}]
unknown_field {[[1 2 3 4 5] [10 20 30 40 50] [100 200 300 400 500]] [[11 21 31 41 51]] [[12 22 32 42 52] [14 44 34 44 54]]}

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