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Marshalling nested json objects on GO lang

I have a struct

type MyStruct struct {
  A string
  B int
  C string
  D int
}

And I want to convert it into a json object like this:

{
  "A": "Some string",
  "B": 1234,
  "otherStruct": {
    "C": "Other string",
    "D": 5678
  }
}

What json tags do I need to use to convert it properly?

I tried to add some json tags like this:

type MyStruct struct {
  A string  `json:"A"`
  B int     `json:"B"`
  C string  `json:"otherStruct.C"`
  D int     `json:"otherStruct.D"`
}

But it results in this:

{
  "A": "Some string",
  "B": 1234,
  "otherStruct.C": "Other string",
  "otherStruct.D": 5678
}
Tags:

2

Answers


  1. 0

    If you want this JSON output using the standard Go JSON package:

    {
  "A": "Some string",
  "B": 1234,
  "otherStruct": {
    "C": "Other string",
    "D": 5678
  }
}

    Then you will need to rewrite your Go structures to match the structure of the JSON. E.g:

    package main

import (
    "encoding/json"
    "fmt"
)

type (
    OtherStruct struct {
        C string
        D int
    }

    MyStruct struct {
        A           string
        B           int
        OtherStruct OtherStruct `json:"otherStruct"`
    }
)

func main() {
    myvar := MyStruct{
        A: "Some string",
        B: 1234,
        OtherStruct: OtherStruct{
            C: "Other string",
            D: 5678,
        },
    }

    jsontext, err := json.Marshal(myvar)
    if err != nil {
        panic(err)
    }

    fmt.Printf("%sn", jsontext)
}

    This will produce:

    {
  "A": "Some string",
  "B": 1234,
  "otherStruct": {
    "C": "Other string",
    "D": 5678
  }
}

    I don’t believe there’s any way with the standard tooling to have the structure of the JSON be different from the structure of your variables.

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  2. 0

    While @larsks answer will work for you. Another option is to define a struct inside another struct.

    type MyStruct struct {
    A     string `json:"A"`
    B     int    `json:"B"`
    Other struct {
        C string `json:"C"`
        D int    `json:"D"`
    } `json:"otherStruct"`
}

    But than you have to assign values to nested struct separately.

    data := MyStruct{
    A: "example A",
    B: 1,
}

// Set values inside Other struct
data.Other.C = "example C"
data.Other.D = 2

    This will give you same output:

    {
"A": "example A",
"B": 1,
"otherStruct": {
    "C": "example C",
    "D": 2
    }
}
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