JSON nested struct to itself in Go Language

Question

I have below JSON

[{
  "id": 8,
  "title": "Indonesia",
  "type": "country",
  "attributes": {
    "regionCode": "ID",
    "information": {
      "title": "Welcome to Indonesia",
      "content": "We only serve selected areas in Indonesia.",
      "image": "indo.png"
    }
  },
  "children": [
    {
      "id": 9,
      "title": "Jakarta",
      "type": "city",
      "attributes": {
        "regionCode": "ID-JKT",
        "information": {
          "title": "Welcome to Capital City of Indonesia",
          "content": "We only serve selected areas in Jabotabek",
          "image": "jakarta.png"
        }
      }       
    },
    {
      "id": 10,
      "title": "Bali",
      "type": "city",
      "attributes": {
        "regionCode": "ID-BAL",
        "information": {
          "title": "Welcome to the beach city Bali",
          "content": "We only serve selected areas in Bali.",
          "image": "bali.png"
        }   
      }       
    }
  ]
}]

Technically this is a nested structure to itself as the children node, and the children might have children as well. But i just couldnt get it right when im using unmarshal to decode this.

The working one is like below i have no problem defining the attribute as a separate struct so assuming i have locationAttribute struct

type locationNode []struct {
    ID         string             `json:"id"`
    Title      string             `json:"title"`
    Type       string             `json:"type"`
    Attributes locationAttribute `json:"attributes"`
    Children   []struct {
        ID         string             `json:"id"`
        Title      string             `json:"title"`
        Type       string             `json:"type"`
        Attributes locationAttribute `json:"attributes"`
        Children   []interface{}      `json:"children"`
    } `json:"children"`
}

However im expecting to be something like below

type locationNode []struct {
    ID         string             `json:"id"`
    Title      string             `json:"title"`
    Type       string             `json:"type"`
    Attributes locationAttribute `json:"attributes"`
    Children   []locationNode `json:"children"`
}

any help will be much appreciated

What is the question? You can use Children []locationNode and it will work. — icza
– icza, Commented Jan 6, 2017 at 9:56
umm but i got an error {"error":"json: cannot unmarshal object into Go value of type []address.locationNode"} — Fandy Dharmawan
– Fandy Dharmawan, Commented Jan 6, 2017 at 10:08

icza · Accepted Answer · 2017-01-06 10:21:31Z

Besides the fact that in the JSON text the "id" field is a number and not string, it works for me.

Omitting the "attributes" to make the example shorter:

type locationNode struct {
    ID       int            `json:"id"`
    Title    string         `json:"title"`
    Type     string         `json:"type"`
    Children []locationNode `json:"children"`
}

func main() {
    ln := locationNode{}

    err := json.Unmarshal([]byte(src), &ln)

    fmt.Printf("%+v %v\n", ln, err)
}

const src = `{
  "id": 8,
  "title": "Indonesia",
  "type": "country",
  "attributes": {
    "regionCode": "ID",
    "information": {
      "title": "Welcome to Indonesia",
      "content": "We only serve selected areas in Indonesia.",
      "image": "indo.png"
    }
  },
  "children": [
    {
      "id": 9,
      "title": "Jakarta",
      "type": "city",
      "attributes": {
        "regionCode": "ID-JKT",
        "information": {
          "title": "Welcome to Capital City of Indonesia",
          "content": "We only serve selected areas in Jabotabek",
          "image": "jakarta.png"
        }
      }       
    },
    {
      "id": 10,
      "title": "Bali",
      "type": "city",
      "attributes": {
        "regionCode": "ID-BAL",
        "information": {
          "title": "Welcome to the beach city Bali",
          "content": "We only serve selected areas in Bali.",
          "image": "bali.png"
        }   
      }       
    }
  ]
}`

Output (try it on the Go Playground):

{ID:8 Title:Indonesia Type:country Children:[{ID:9 Title:Jakarta Type:city Children:[]} {ID:10 Title:Bali Type:city Children:[]}]} <nil>

Franck Jeannin · Accepted Answer · 2017-01-06 13:04:21Z

1

Using https://mholt.github.io/json-to-go/ your JSON converts to

type AutoGenerated struct {
    ID int `json:"id"`
    Title string `json:"title"`
    Type string `json:"type"`
    Attributes struct {
        RegionCode string `json:"regionCode"`
        Information struct {
            Title string `json:"title"`
            Content string `json:"content"`
            Image string `json:"image"`
        } `json:"information"`
    } `json:"attributes"`
    Children []struct {
        ID int `json:"id"`
        Title string `json:"title"`
        Type string `json:"type"`
        Attributes struct {
            RegionCode string `json:"regionCode"`
            Information struct {
                Title string `json:"title"`
                Content string `json:"content"`
                Image string `json:"image"`
            } `json:"information"`
        } `json:"attributes"`
    } `json:"children"`
}

edited Jan 6, 2017 at 13:04

answered Jan 6, 2017 at 9:54

Franck Jeannin

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2 Comments

Fandy Dharmawan Over a year ago

Thanks for your comment but this is not ideal bcoz technically the children could have children and so on. "children": [ { "id": 9, "title": "Jakarta", "type": "city", "attributes": {}, "children": [{},{},{}] },...

Franck Jeannin Over a year ago

It's important to know that the tool exists plus it should give you a head start in customizing it to your need.

Vatine · Accepted Answer · 2017-01-06 10:29:12Z

0

It certainly looks like defining Children in the way you expect works fine. The following both marshals and unmarshals fine.

type Bob struct {
    ID         string            `json:"id"`
    Title      string            `json:"title"`
    Type       string            `json:"type"`
    Attributes int               `json:"attributes"`
    Children   []Bob             `json:"children"`
}

Playground link

answered Jan 6, 2017 at 10:29

Vatine

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Comments

ain · Accepted Answer · 2017-01-06 11:48:29Z

0

Okay I managed to resolve this - it's actually a silly careless mistake, since my struct is already an array I should NOT define the children as an array.

So below definition works

type locationNode []struct {
  ID         string             `json:"id"`
  Title      string             `json:"title"`
  Type       string             `json:"type"`
  Attributes locationAttribute  `json:"attributes"`
  Children   locationNode     `json:"children"`
}

edited Jan 6, 2017 at 11:48

ain

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answered Jan 6, 2017 at 10:19

Fandy Dharmawan

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