The empty interface

Context

The empty interface interface{} (or any in Go 1.18+) has zero methods. Therefore every type satisfies it. It is used when a function can accept values of any type, similar to any in TypeScript. However, to use the underlying value, you must perform a type assertion or type switch.

Example

Accept any value and print it using fmt.Println (which already takes any).

Code example

package main

import "fmt"

func describe(i interface{}) {
    fmt.Printf("Type = %T, Value = %v\n", i, i)
}

func main() {
    describe(42)
    describe("hello")
    describe(3.14)
}

Output

Type = int, Value = 42
Type = string, Value = hello
Type = float64, Value = 3.14

Useful links

• Go spec: Empty interface
• Go by Example: Empty Interface