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:
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:
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:
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:
{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:
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:
{ "ID": 42, "Title": "Example title", "List": [ 1, 2, 3 ] }
Further Reading
- The Go maps in action blog post
- The zero value in the Go Spec
- The empty struct by Dave Cheney
- SentryGo Error Tracking and Performance Monitoring
- Syntax.fmListen to the Syntax Podcast
- Listen to the Syntax Podcast
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