Support embedded dynamic struct

[leslie-qiwa]

Thanks for making this great tool. It is very useful for GraphQL query which requires dynamic struct sometimes.

One feature seems missing is not supported embedded dynamic struct. For example,

func main() {
  childStruct := dynamicstruct.NewStruct().
    AddField("Child", 0, `json:"int"`).
    Build()

  childInstance := childStruct.New()
  content, err := json.Marshal(childInstance)
  if err != nil {
    log.Fatal(err)
  }
  fmt.Println(string(content))

  parentStruct := dynamicstruct.NewStruct().
    AddField("Parent", &childInstance, "").Build()

  parentInstance := parentStruct.New()
  content, err = json.Marshal(parentInstance)
  if err != nil {
    log.Fatal(err)
  }

  fmt.Println(string(content))
}

Result will be:

{"int":0}
{"Parent":null}

Seems like this is due to embedded dynamic struct instance is not initialized, so if explicitly init like below, it will marshal correctly

func main() {
        childStruct := dynamicstruct.NewStruct().
                AddField("Child", 0, `json:"int"`).
                Build()

        childInstance := childStruct.New()
        content, err := json.Marshal(childInstance)
        if err != nil {
                log.Fatal(err)
        }
        fmt.Println(string(content))

        parentStruct := dynamicstruct.NewStruct().
                AddField("Parent", &childInstance, "").Build()

        parentInstance := parentStruct.New()

                data := []byte(`
                {
                        "Parent": {
                          "Child": 0
                        }
                }
                `)

                err = json.Unmarshal(data, &parentInstance)
                if err != nil {
                        log.Fatal(err)
                }

        content, err = json.Marshal(parentInstance)
        if err != nil {
                log.Fatal(err)
        }

        fmt.Println(string(content))
}

Marshal result is

{"int":0}
{"Parent":{"Child":0}}

[mtt0]

See #21

[PBholewasi]

This is still not working