Go Interfaces

An interface lists methods. Any type that has those methods satisfies it automatically: there is no implements keyword.

ExampleGo

package main

import (
  "fmt"
  "math"
)

type Shape interface {
  Area() float64
}

type Circle struct{ R float64 }
type Rect struct{ W, H float64 }

func (c Circle) Area() float64 { return math.Pi * c.R * c.R }
func (r Rect) Area() float64   { return r.W * r.H }

func main() {
  shapes := []Shape{Circle{1}, Rect{2, 3}}
  for _, s := range shapes {
    fmt.Printf("%.2f\n", s.Area())
  }
}

Output

3.14
6.00

Quick check

How does a Go type satisfy an interface?

By declaring implementsBy having the right methodsBy embedding it

Finish the quick check (and any code exercise) to complete this lesson, or mark it done yourself.

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