Anonymous Structs

An anonymous struct describes a small record directly where it is used, without first declaring a named struct type.

The expression struct { ID int; Active bool }{ID: 7, Active: true} combines a struct type and a literal. It can be useful for one-off grouping, tests and locally scoped data.

Anonymous structs still have well-defined field names and types. If the same shape is used throughout a package or has behavior attached to it, a named struct type is generally clearer.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import "fmt"

func main() {
	status := struct {
		Code   int
		Active bool
	}{
		Code:   200,
		Active: true,
	}
	fmt.Println("Code:", status.Code)
	fmt.Println("Active:", status.Active)
}

Output

Code: 200
Active: true

The anonymous struct has two fields initialized by a keyed literal. The dot operator accesses those fields just as it would on a named struct.

• An anonymous struct is not an untyped map.
• Repeated complex anonymous struct declarations can obscure the model; use a named type when appropriate.

Create an anonymous struct holding a task name and a completion flag. Update the flag and print both fields.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Anonymous Structs in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.