Parsing arbitrary JSON with go

json-parsing.go

package main

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

func main() {
  b := []byte(`{"name": "tom", "favNum": 6, "interests": ["knives", "computers"], "usernames": {"github": "TomNomNom", "twitter": "@TomNomNom"}}`)
  var f interface{}
  err := json.Unmarshal(b, &f) 
  if err != nil {
    log.Fatal("Failed to parse JSON")
  }

  m := f.(map[string]interface{})

  printStruct("", m)

}

func printStruct(prefix string, m map[string]interface{}) {
  for k, v := range m { 
    switch vv := v.(type) {
    case string:
      fmt.Println(prefix, k, "is string", vv) 
    case float64:
      fmt.Println(prefix, k, "is number", vv) 
    case []interface{}:
      fmt.Println(prefix, k, "is an array:")
      for i, u := range vv {
        fmt.Println(prefix, i, u)
      }   
    case map[string]interface{}:
      fmt.Println(prefix, k, "is a map:")
      printStruct(prefix + "  ", vv) 
    default:
      fmt.Println(prefix, k, "is a type we can't handle", vv) 
    }   
  }
}