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How To Print Struct Fields in Go

How To Print Struct Fields in Go

Clive B.

—

The Problem

You don’t know how to see the values that a struct contains.

The Solution

Because struct fields in Go are just values, printing them out can be as simple as printing any variable:

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package main

import "fmt"

type Example struct {
    ID    int
    Title string
}

func main() {
    example := Example{
        ID:    42,
        Title: "Example title",
    }

    fmt.Printf("example struct: ID: %d, Title: %s", example.ID, example.Title)

This prints:

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example struct: ID: 42, Title: Example title

Printing the Entire Struct

If you want to print the entire struct and include its field names automatically, you can use a special verb to do so:

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package main

import (
    "encoding/json"
    "fmt"
    "log"
)

type Example struct {
    ID    int
    Title string
    List  []int
}

func main() {
    example := Example{
        ID:    42,
        Title: "Example title",
        List:  []int{1, 2, 3},
    }

    fmt.Printf("%+v", example)
}

This prints:

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{ID:42 Title:Example title List:[1 2 3]}

Alternatively, if you want to print something easier to see over multiple lines, you can use the json.MarshallIndent function to print it as indented JSON:

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func main() {
    example := Example{
        ID:    42,
        Title: "Example title",
        List:  []int{1, 2, 3},
    }

    bytes, err := json.MarshalIndent(example, "", "\t")
    if err != nil {
        log.Fatal("failed to marshal example", err)
    }

    fmt.Println(string(bytes))
}

This prints:

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{
  "ID": 42,
  "Title": "Example title",
  "List": [
    1,
    2,
    3
  ]
}

Further Reading

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