How to parse json object and print particular value

Question

I have json object that consists sub object of array. how can I print particular sub object in json. here is my code

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    //Simple Employee JSON which we will parse
    empArray := `{"meta":[
        {
            "id": 1,
            "name": "Mr. Boss",
            "department": "",
            "designation": "Director"
        },
        {
            "id": 11,
            "name": "Irshad",
            "department": "IT",
            "designation": "Product Manager"
        },
        {
            "id": 12,
            "name": "Pankaj",
            "department": "IT",
            "designation": "Team Lead"
        }
    ]}`

    // Declared an empty interface of type Array
    var results []map[string]interface{}

    // Unmarshal or Decode the JSON to the interface.
    json.Unmarshal([]byte(empArray['meta']), &results)

    fmt.Println(results)
}

I'm getting below error while doing soo..

./test.go:35:23: cannot convert empArray['\u0000'] (type byte) to type []byte
./test.go:35:33: invalid character literal (more than one character)

with in the empArray array object, I wanted to print meta object that consists array of employees. Please help me to accomplish this.

score 2 · Accepted Answer · edited Feb 28 '20 at 07:54

2

You are almost there. Parse the entire document and then pick out the part you want.

    var results map[string][]interface{}
    json.Unmarshal([]byte(empArray), &results)
    fmt.Println(results["meta"])

edited Feb 28 '20 at 07:54

Adirio

5,040
1
14
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answered Feb 28 '20 at 06:57

Bryce Donovan

36
1

Thanks Bryce Donovan for your quick answer. – ajay Feb 28 '20 at 07:08
Please let me know how we can do the same if we have object of objects in `meta` object just like below.```{"meta":{"data":[ { "id": 1, "name": "Mr. Boss", "department": "", "designation": "Director" }, { "id": 11, "name": "Irshad", "department": "IT", "designation": "Product Manager" }, { "id": 12, "name": "Pankaj", "department": "IT", "designation": "Team Lead" } ]}}``` – ajay Feb 28 '20 at 07:09
@ajay In my answer I provided the Go way of unmarshalling JSON objects including the new syntax you mention here. – Adirio Feb 28 '20 at 07:50
yeah you are right. but my question is like, how can we get nested object data. here, I wanted to get `data` object that is nested by `meta`. Im trying this `var results map[string][]interface{} json.Unmarshal([]byte(empArray), &results) fmt.Println(results["meta"]['data'])`. but Im getting error 'more than one character literal'. is it correct? – ajay Feb 28 '20 at 08:03
Single quotes (`'`) and double quotes (`"`) are not interchangeable in Go. https://play.golang.org/p/JsQUZhZWExj shows how using `'` yields the same error. The problem is not related with parsing JSON, but with Go basics. Please follow the Go Tour: https://tour.golang.org/welcome/1 – Adirio Mar 02 '20 at 08:11

Adirio · Answer 2 · 2020-02-28T08:27:06.793

You should use custom structs:

type Employee struct {
    ID          int    `json:"id"`
    Name        string `json:"name"`
    Department  string `json:"department"`
    Designation string `json:"designation"`
}

type Employees struct {
    Meta []Employee `json:"meta"`
}

When you try to unmarshal the provided string into a Employees var it will read the annotations and know where to place each field. You can find the working example at Golang Playground. I added a string representation to the Employee struct so that fmt.Println output is more redable.

In the case of having an extra nested key ({meta: {data: [...]}}), the types would be as follows:

type Employee struct {
    ID          int    `json:"id"`
    Name        string `json:"name"`
    Department  string `json:"department"`
    Designation string `json:"designation"`
}

type EmployeesData struct {
    Data []Employee `json:"data"`
}

type Employees struct {
    Meta EmployeesData `json:"meta"`
}

You can find the working example at Golang Playground too.

NOTE: I do not have context to name the structs properly, so I used Employees and EmployeesData but you should use more descriptive names that help understanding what the whole object represents and not only the meta and data fields.

Hello Adirio, thanks for your answer. but I just don't wanna create separate struct template for every object. @Bryce Donovan's answer seems somewhat relatable to me without creating struct template. I asked him a question in the comments about nested object and please answer it if possible without creating struct templates — ajay, Feb 28 '20 at 10:08
Hi Ajay, creating structs is how it should be done in Go. Using maps and slices of `interface{}` would require a lot of checks that are already handled by the structs themselves as they know the type. By using maps and slices of `interface{}`, it seems like you are trying to program in Go like if it was Python or JS. — Adirio, Mar 02 '20 at 08:31

How to parse json object and print particular value

2 Answers2