Interface values

Under the hood, interface values can be thought of as a tuple of a value and a concrete type: 

  1. (value, type)

An interface value holds a value of a specific underlying concrete type.

Calling a method on an interface value executes the method of the same name on its underlying type.

interface-values.go

  1. package main
  3. import (
  4.     "fmt"
  5.     "math"
  6. )
  8. type I interface {
  9.     M()
  10. }
  12. type T struct {
  13.     S string
  14. }
  16. func (t *T) M() {
  17.     fmt.Println(t.S)
  18. }
  20. type F float64
  22. func (f F) M() {
  23.     fmt.Println(f)
  24. }
  26. func main() {
  27.     var i I
  29.     i = &T{"Hello"}
  30.     describe(i)
  31.     i.M()
  33.     i = F(math.Pi)
  34.     describe(i)
  35.     i.M()
  36. }
  38. func describe(i I) {
  39.     fmt.Printf("(%v, %T)\n", i, i)
  40. }