dictionary - Decode arbitrary JSON in Golang -

i have question decoding arbitrary json objects/messages in go.. lets example have 3 wildly different json objects (aka messages) can receive on http connection, lets call them sake of illustration:

{ home : { unique set of arrays, objects, fields, , arrays objects } } 

and

{ bike : { unique set of arrays, objects, fields, , arrays objects } } 

and

{ soda : { unique set of arrays, objects, fields, , arrays objects } } 

what thinking decode these, http connection in map of interfaces such as:

func httpserverhandler(w http.responsewriter, r *http.request) {     message := make(map[string]interface{})     decoder := json.newdecoder(r.body)     _ = decoder.decode(&message) 

then if, else if block valid json messages

if _, ok := message["home"]; ok {     // decode interface{} appropriate struct } else if _, ok := message["bike"]; ok {     // decode interface{} appropriate struct } else {     // decode interface{} appropriate struct } 

now in if block can make work if re-decode entire package, thinking kind of waste since have partially decoded , need decode value of map interface{}, can not seem work right.

redecoding entire thing works though, if following hometype example struct:

var homeobject hometype var bikeobject biketype var sodaobject sodatype 

then in if block do:

if _, ok := message["home"]; ok {     err = json.unmarshal(r.body, &homeobject)     if err != nil {         fmt.println("bad response, unable decode json message contents")         os.exit(1)     } 

so without re-decoding / unmarshal-ing entire thing again, how work interface{} in map?

if have map[string]interface{} can access values using type assertions, e.g.

home, valid := msg["home"].(string) if !valid {     return } 

this works nicely simple values. more complicated nested structures might find easier deferred decoding json.rawmessage or implement custom json.unmarshaler. see this detailed discussion.

another idea might define custom message type consisting of pointers home, bike, , soda structs. such as

type home struct {     homestuff     int     morehomestuff string }   type bike struct {     bikestuff int }  type message struct {     bike *bike `json:"bike,omitempty"`     home *home `json:"home,omitempty"` } 

if set these omit if nil unmarshalling should populate relevant one. can play here.