How to print struct variables in console?

To print the name of the fields in a struct:

fmt.Printf("%+v\n", yourProject)

From the fmt package:

when printing structs, the plus flag (%+v) adds field names

That supposes you have an instance of Project (in 'yourProject')

The article JSON and Go will give more details on how to retrieve the values from a JSON struct.

This Go by example page provides another technique:

type Response2 struct {
  Page   int      `json:"page"`
  Fruits []string `json:"fruits"`
}

res2D := &Response2{
    Page:   1,
    Fruits: []string{"apple", "peach", "pear"}}
res2B, _ := json.Marshal(res2D)
fmt.Println(string(res2B))

That would print:

{"page":1,"fruits":["apple","peach","pear"]}

If you don't have any instance, then you need to use reflection to display the name of the field of a given struct, as in this example.

type T struct {
    A int
    B string
}

t := T{23, "skidoo"}
s := reflect.ValueOf(&t).Elem()
typeOfT := s.Type()

for i := 0; i < s.NumField(); i++ {
    f := s.Field(i)
    fmt.Printf("%d: %s %s = %v\n", i,
        typeOfT.Field(i).Name, f.Type(), f.Interface())
}

---

I want to recommend go-spew, which according to their github "Implements a deep pretty printer for Go data structures to aid in debugging"

go get -u github.com/davecgh/go-spew/spew

usage example:

package main

import (
    "github.com/davecgh/go-spew/spew"
)

type Project struct {
    Id      int64  `json:"project_id"`
    Title   string `json:"title"`
    Name    string `json:"name"`
    Data    string `json:"data"`
    Commits string `json:"commits"`
}

func main() {

    o := Project{Name: "hello", Title: "world"}
    spew.Dump(o)
}

output:

(main.Project) {
 Id: (int64) 0,
 Title: (string) (len=5) "world",
 Name: (string) (len=5) "hello",
 Data: (string) "",
 Commits: (string) ""
}

---

my 2cents would be to use json.MarshalIndent -- surprised this isn't suggested, as it is the most straightforward. for example:

func prettyPrint(i interface{}) string {
    s, _ := json.MarshalIndent(i, "", "\t")
    return string(s)
}

no external deps and results in nicely formatted output.

---

I think it would be better to implement a custom stringer if you want some kind of formatted output of a struct

for example

package main

    import "fmt"

    type Project struct {
        Id int64 `json:"project_id"`
        Title string `json:"title"`
        Name string `json:"name"`
    }

    func (p Project) String() string {
        return fmt.Sprintf("{Id:%d, Title:%s, Name:%s}", p.Id, p.Title, p.Name)
    }

    func main() {
        o := Project{Id: 4, Name: "hello", Title: "world"}
        fmt.Printf("%+v\n", o)
    }

---

p = Project{...}
fmt.Printf("%+v", p)
fmt.Printf("%#v", p) //with type

---

Alternatively, try using this function PrettyPrint()

// print the contents of the obj
func PrettyPrint(data interface{}) {
    var p []byte
    //    var err := error
    p, err := json.MarshalIndent(data, "", "\t")
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Printf("%s \n", p)
}

In order to use this you do not need any additional packages with the exception of fmt and encoding/json, just a reference, pointer to, or literal of the struct you have created.

To use just take your struct, initialize it in main or whatever package you are in and pass it into PrettyPrint().

type Prefix struct {
    Network string
    Mask    int
}

func valueStruct() {
    // struct as a value
    var nw Prefix
    nw.Network = "10.1.1.0"
    nw.Mask = 24
    fmt.Println("### struct as a pointer ###")
    PrettyPrint(&nw)
}

It's output would be

### struct as a pointer ###
{
    "Network": "10.1.1.0",
    "Mask": 24
} 

Play around with the code here.

---

It is very convenient to use package fmt to output:

fmt.Printf("%+v \n", yourProject)

if you want to see the full type of the sturct, you can use # replace + :

fmt.Printf("%#v \n", yourProject) 

---

I recommend to use Pretty Printer Library. In that you can print any struct very easily.

Install Library https://github.com/kr/pretty

or

go get github.com/kr/pretty

Now do like this in your code

package main

import (
fmt
github.com/kr/pretty
)

func main(){

type Project struct {
    Id int64 `json:"project_id"`
    Title string `json:"title"`
    Name string `json:"name"`
    Data Data `json:"data"`
    Commits Commits `json:"commits"`
}

fmt.Printf("%# v", pretty.Formatter(Project)) //It will print all struct details

fmt.Printf("%# v", pretty.Formatter(Project.Id)) //It will print component one by one.

}

Also you can get difference between component through this library and so more. You can also have a look on library Docs here.

---

I like litter.

From their readme:

type Person struct {
  Name   string
  Age    int
  Parent *Person
}

litter.Dump(Person{
  Name:   "Bob",
  Age:    20,
  Parent: &Person{
    Name: "Jane",
    Age:  50,
  },
})

Sdump is pretty handy in tests:

func TestSearch(t *testing.T) {
  result := DoSearch()

  actual := litterOpts.Sdump(result)
  expected, err := ioutil.ReadFile("testdata.txt")
  if err != nil {
    // First run, write test data since it doesn't exist
        if !os.IsNotExist(err) {
      t.Error(err)
    }
    ioutil.Write("testdata.txt", actual, 0644)
    actual = expected
  }
  if expected != actual {
    t.Errorf("Expected %s, got %s", expected, actual)
  }
}

---

To print the struct as JSON:

fmt.Printf("%#v\n", yourProject)

Also possible with (as it was mentioned above):

fmt.Printf("%+v\n", yourProject)

But the second option prints string values without "" so it is harder to read.

---

When you have more complex structures, you might need to convert to JSON before printing:

// Convert structs to JSON.
data, err := json.Marshal(myComplexStruct)
fmt.Printf("%s\n", data)

Source: https://gist.github.com/tetsuok/4942960

---

You can do the json mashal first and print it as a string. There you can see it the whole struct value completely.

package main

import "fmt"
import "json"

type Project struct {
    Id int64 `json:"project_id"`
    Title string `json:"title"`
    Name string `json:"name"`
}

func main() {
    o := Project{Id: 4, Name: "hello", Title: "world"}
    om, _ := json.marshal(o)
    log.Printf("%s\n", string(om))
}

---

Sometimes, it might be handy to print the struct as valid Go code (the go/ast equivalent). For this purpose, https://github.com/hexops/valast does a great job:

package main

import (
    "fmt"

    "github.com/hexops/valast"
)

type ProjectData struct {
    Title   string `json:"title"`
    Name    string `json:"name"`
    Data    string `json:"data"`
    Commits string `json:"commits"`
}

type Project struct {
    Id   int64        `json:"project_id"`
    Data *ProjectData `json:"data"`
}

func main() {
    p := Project{
        Id: 1,
        Data: &ProjectData{
            Title:   "Test",
            Name:    "Mihai",
            Data:    "Some data",
            Commits: "Test Message",
        },
    }
    fmt.Println(valast.String(p))
}

Output:

go run main.go 
Project{Id: 1, Data: &ProjectData{
        Title:   "Test",
        Name:    "Mihai",
        Data:    "Some data",
        Commits: "Test Message",
}}

---

Visit here to see the complete code. Here you will also find a link for an online terminal where the complete code can be run and the program represents how to extract structure's information(field's name their type & value). Below is the program snippet that only prints the field names.

package main

import "fmt"
import "reflect"

func main() {
    type Book struct {
        Id    int
        Name  string
        Title string
    }

    book := Book{1, "Let us C", "Enjoy programming with practice"}
    e := reflect.ValueOf(&book).Elem()

    for i := 0; i < e.NumField(); i++ {
        fieldName := e.Type().Field(i).Name
        fmt.Printf("%v\n", fieldName)
    }
}

/*
Id
Name
Title
*/

---

i suggest to use json.Unmarshal() i try to print the id with this hope its helpfull:

var jsonString = `{"Id": 1, "Title": "the title", "Name": "the name","Data": "the data","Commits" : "the commits"}`
var jsonData = []byte(jsonString)

var data Project

var err = json.Unmarshal(jsonData, &data)
if err != nil {
    fmt.Println(err.Error())
    return
}

fmt.Println("Id :", data.Id)

---

Maybe this shouldn't be applied for production requests but if you are on debugging mode I suggest you follow the below approach.

marshalledText, _ := json.MarshalIndent(inputStruct, "", " ")
fmt.Println(string(marshalledText))

This results in formatting the data in json format with increased readability.

---

There's also go-render, which handles pointer recursion and lots of key sorting for string and int maps.

Installation:

go get github.com/luci/go-render/render

Example:

type customType int
type testStruct struct {
        S string
        V *map[string]int
        I interface{}
}

a := testStruct{
        S: "hello",
        V: &map[string]int{"foo": 0, "bar": 1},
        I: customType(42),
}

fmt.Println("Render test:")
fmt.Printf("fmt.Printf:    %#v\n", a)))
fmt.Printf("render.Render: %s\n", Render(a))

Which prints:

fmt.Printf:    render.testStruct{S:"hello", V:(*map[string]int)(0x600dd065), I:42}
render.Render: render.testStruct{S:"hello", V:(*map[string]int){"bar":1, "foo":0}, I:render.customType(42)}

---

fmt.Printf("%+v\n", project)

This is the basic way of printing the details

---

very simple I don't have the structure of Data and Commits So I changed the

package main

import (
    "fmt"
)

type Project struct {
    Id      int64   `json:"project_id"`
    Title   string  `json:"title"`
    Name    string  `json:"name"`
    Data    string  `json:"data"`
    Commits string  `json:"commits"`
}

func main() {
    p := Project{
    1,
    "First",
    "Ankit",
    "your data",
    "Commit message",
    }
    fmt.Println(p)
}

For learning you can take help from here : https://gobyexample.com/structs

---

If you want to write in a log file, as I was searching previously. Then you should use:

log.Infof("Information %+v", structure)

Note:: This will not work with log.Info or log.Debug. In this case, "%v" will get printed, and all the values of the structure will be printed without printing the key/variable name.

---

A lot of answers for a simple question. I might as well throw my hat in the ring.

package main

import "fmt"

type Project struct {
    Id    int64  `json:"project_id"`
    Title string `json:"title"`
    Name  string `json:"name"`
    //Data    Data    `json:"data"`
    //Commits Commits `json:"commits"`
}

var (
    Testy Project
)

func dump_project(foo Project) {
    fmt.Println("== Dump Project Struct ====")
    fmt.Printf("Id: %d\n", foo.Id)
    fmt.Println("Title: ", foo.Title)
    fmt.Printf("Name: %v\n", foo.Name)
}

func main() {
    fmt.Println("hello from go")
    Testy.Id = 3
    Testy.Title = "yo"
    Testy.Name = "my name"
    fmt.Println(Testy)
    dump_project(Testy)
}

The output of the various print methods

hello from go
{3 yo my name}
== Dump Project Struct ====
Id: 3
Title:  yo
Name: my name

---

Without using external libraries and with new line after each field:

log.Println(
            strings.Replace(
                fmt.Sprintf("%#v", post), ", ", "\n", -1))

---

    type Response struct {
        UserId int    `json:"userId"`
        Id     int    `json:"id"`
        Title  string `json:"title"`
        Body   string `json:"body"`
    }

    func PostsGet() gin.HandlerFunc {
        return func(c *gin.Context) {
            xs, err := http.Get("https://jsonplaceholder.typicode.com/posts")
            if err != nil {
                log.Println("The HTTP request failed with error: ", err)
            }
            data, _ := ioutil.ReadAll(xs`enter code here`.Body)


            // this will print the struct in console            
            fmt.Println(string(data))


            // this is to send as response for the API
            bytes := []byte(string(data))
            var res []Response
            json.Unmarshal(bytes, &res)

            c.JSON(http.StatusOK, res)
        }
    }

---

Another way is, create a func called toString that takes struct, format the fields as you wish.

import (
    "fmt"
)

type T struct {
    x, y string
}

func (r T) toString() string {
    return "Formate as u need :" + r.x + r.y
}

func main() {
    r1 := T{"csa", "ac"}
    fmt.Println("toStringed : ", r1.toString())
}

---

Most of these packages are relying on the reflect package to make such things possible.

https://i.stack.imgur.com/3h9Kr.png

fmt.Sprintf() is using -> func (p *pp) printArg(arg interface{}, verb rune) of standard lib

Go to line 638 -> https://golang.org/src/fmt/print.go

Reflection:

https://golang.org/pkg/reflect/

Example code:

https://github.com/donutloop/toolkit/blob/master/debugutil/prettysprint.go

---

fmt.Println("%+v", structure variable)

A better way to do this would be to create a global constant for the string "%+v" in a package called "commons"(maybe) and use it everywhere in your code

//In commons package
const STRUCTURE_DATA_FMT = "%+v"

//In your code everywhere
fmt.Println(commons.STRUCTURE_DATA_FMT, structure variable)

---