Go - The map[string]interface{} map

Remember that the biggest advantage you get from using a map[string]interface{} map, or any map that stores an interface{} value in general, is that you still have your data in its original state and data type.

Nowadays, web services work by exchanging JSON records. If you get a JSON record in an anticipated format, then you can process it as expected and everything will be fine. However, there are times when you might get an erroneous record or a record in an unsupported JSON format. In these cases, using map[string]interface{} for storing these unknown JSON records (arbitrary data) is a good choice because map[string]interface{} is good at storing JSON records of unknown types.

 

package main

import (
    "encoding/json"
    "fmt"
    "os"
)

var JSONrecord = `{
    "Flag": true,
    "Array": ["a","b","c"],
    "Entity": {
        "a1": "b1",
        "a2": "b2",
        "Value": -456,
        "Null": null
    },
    "Message": "Hello Go!"
}`

func typeSwitch(m map[string]interface{}) {
    for k, v := range m {
        switch c := v.(type) {
        case string:
            fmt.Println("Is a string!", k, c)
        case float64:
            fmt.Println("Is a float64!", k, c)
        case bool:
            fmt.Println("Is a Boolean!", k, c)
        case map[string]interface{}:
            fmt.Println("Is a map!", k, c)
            typeSwitch(v.(map[string]interface{}))
        default:
            fmt.Printf("...Is %v: %T!\n", k, c)
        }
    }
}

func exploreMap(m map[string]interface{}) {
    for k, v := range m {
        embMap, ok := v.(map[string]interface{})
        // If it is a map, explore deeper
        if ok {
            fmt.Printf("{\"%v\": \n", k)
            exploreMap(embMap)
            fmt.Printf("}\n")
        } else {
            fmt.Printf("%v: %v\n", k, v)
        }
    }
}

func main() {
    if len(os.Args) == 1 {
        fmt.Println("*** Using default JSON record.")
    } else {
        JSONrecord = os.Args[1]
    }
    JSONMap := make(map[string]interface{})
    err := json.Unmarshal([]byte(JSONrecord), &JSONMap)
    if err != nil {
        fmt.Println(err)
        return
    }
    exploreMap(JSONMap)
    fmt.Println("------------------------------------------------")
    typeSwitch(JSONMap)
}