如何解组未知字段名称的JSON以构造[重复]

Question

This question already has an answer here:

• Unmarshal JSON with unknown fields [duplicate] 7 answers

Is it possible to unmarshal JSON with unknown field? That field name is always different, but the structure is the same. JSON is a result of POST request.

My 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 MyStruct struct {
    MainData map[string]mData `json:"-"`
}

type mData struct {
    knownField1 [][5]int `json:"known_field_1"`
    knownField2 [][5]int `json:"known_field_2"`
    knownField3 [][5]int `json:"known_field_3"`
}

func NewMyStruct() MyStruct {
    ms := MyStruct{}
    ms.MainData = make(map[string]mData)
    return ms
}

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

    fmt.Println(myStruct) // gives {map[]}
}

</div>

Answer 1

Simply use a map if you don't know the key, and the value type of the map may be the struct describing the structure:

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

Note that you must export the fields for this to work!

And the unmarshaling code:

var data map[string]mData
if err := json.Unmarshal(body, &data); err != nil {
    panic(err)
}

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

Output (try it on the Go Playground):

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]]}

See related questions:

How to parse/deserlize a dynamic JSON in Golang

Unmarshal JSON with unknown fields

Unmarshal json string to a struct that have one element of the struct itself

JSON Nested dynamic structures Go decoding