Convert json to struct using reflection in golang

Question

func deserialize(request *http.Request,typ reflect.Type) (interface{}, *httpNet.HandlerError){

    data,e:=ioutil.ReadAll(request.Body)
    fmt.Println(string(data))
    if e !=nil{
        return nil,&httpNet.HandlerError{e,"could not read request",http.StatusBadRequest}
    }

    v:=typ.Elem()
    payload:=reflect.New(v).Elem().Interface()

    eaa:= json.NewDecoder(request.Body).Decode(payload)

    if e!=nil{
        fmt.Println(eaa.Error())
    }
    fmt.Println(payload)
    fmt.Println(reflect.ValueOf(payload)
        )
    return payload,nil

}

to call it:

r,_:= deserialize(request,reflect.TypeOf(&testData{}))

It does not throw errors and looks completely valid operation to me , but the result is an empty structure of expecting type.

Whats the problem with that?

Not_a_Golfer · Accepted Answer · 2015-06-14 12:11:59Z

4

The problem is that you are passing a non pointer instance of the type:

payload:=reflect.New(v).Elem().Interface()

Means "allocate a new pointer to the type, then take the value of it, and extract it as interface{}.

You should just keep it at:

payload:=reflect.New(v).Interface()

BTW It's also redundant that you are passing the type of a pointer, extracting its Elem(), then allocating a pointer. Do something like this:

if type.Kind() == reflect.Ptr {
   typ = typ.Elem()
}

payload := reflect.New(typ).Interface()

then you can pass both pointers and non pointers to the function.

Edit: Working playground example: http://play.golang.org/p/TPafxcpIU5

edited Jun 14, 2015 at 12:11

answered Jun 14, 2015 at 10:31

Not_a_Golfer

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3 Comments

Mohsen Over a year ago

tanx , tested it but I got the same result

Not_a_Golfer Over a year ago

@Mohsen I'm doing the exact same thing in my code and it works perfectly. Are you sure there's data coming in?

Not_a_Golfer Over a year ago

@Mohsen I've created a simplified working example in the playground. See the answer's edited text.

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