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Converting Go struct to JSON [duplicate]

stackoverflow.com › questions › 8270816 › converting-go-struct-to-json

You need to export the User.name field so that the json package can see it. Rename the name field to Name.

Copypackage main

import (
    "fmt"
    "encoding/json"
)

type User struct {
    Name string
}

func main() {
    user := &User{Name: "Frank"}
    b, err := json.Marshal(user)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(b))
}

Output:

Copy{"Name":"Frank"}

Answer from peterSO on Stack Overflow

Mholt

mholt.github.io › json-to-go

JSON-to-Go: Convert JSON to Go instantly

This tool instantly converts JSON into a Go type definition. Paste a JSON structure on the left and the equivalent Go type will be generated to the right, which you can paste into your program.

Stack Overflow

stackoverflow.com › questions › 8270816 › converting-go-struct-to-json

Converting Go struct to JSON - Stack Overflow

Top answer

1 of 2

564

You need to export the User.name field so that the json package can see it. Rename the name field to Name.

Copypackage main

import (
    "fmt"
    "encoding/json"
)

type User struct {
    Name string
}

func main() {
    user := &User{Name: "Frank"}
    b, err := json.Marshal(user)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(b))
}

Output:

Copy{"Name":"Frank"}

2 of 2

You can define your own custom MarshalJSON and UnmarshalJSON methods and intentionally control what should be included, ex:

Copypackage main

import (
    "fmt"
    "encoding/json"
)

type User struct {
    name string
}

func (u *User) MarshalJSON() ([]byte, error) {
    return json.Marshal(&struct {
        Name     string `json:"name"`
    }{
        Name:    u.name,
    })
}

func main() {
    user := &User{name: "Frank"}
    b, err := json.Marshal(user)
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(string(b))
}

Discussions

How do you guys convert a json response to go structs?

There are tools that can create a struct out of a json object. https://mholt.github.io/json-to-go/ More on reddit.com

r/golang

January 14, 2024

A tool for generating structs based on json I have

https://mholt.github.io/json-to-go/ More on reddit.com

r/golang

September 26, 2021

What is the best way to handle json in Golang?

If the json is highly unstructured the unmarshal to map[string]any. For unknown structs use json.RawMessage More on reddit.com

r/golang

September 20, 2024

Converting an interface{} to a struct

Looks like you're describing tagged unions. There is an interresting answer on stackoverflow. This is ideal if the content is a child field and the type is on top level, you can just unmarshal the child once you know the type and avoid too much unmarshalling. Still a bit more parsing overhead than the customConverter solution, benchmarking will decide if parsing once to primitives is more expensive than parsing twice the child payload. the following comes from stackoverflow https://stackoverflow.com/questions/55994888/unmarshal-json-tagged-union-in-go : type Request struct { RequestId string Inputs []struct { Intent string Payload json.RawMessage } } var request Request err := json.Unmarshal(j, &request) if err != nil { log.Fatalln("error:", err) } for _, input := range request.Inputs { var payload interface{} switch input.Intent { case "action.devices.EXECUTE": payload = new(Execute) case "action.devices.QUERY": payload = new(Query) } err := json.Unmarshal(input.Payload, payload) if err != nil { log.Fatalln("error:", err) } // Do stuff with payload } More on reddit.com

r/golang

April 6, 2023

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