62 lines
1.4 KiB
Go
62 lines
1.4 KiB
Go
// _Interfaces_ are named collections of method
|
|
// signatures.
|
|
|
|
package main
|
|
|
|
import "fmt"
|
|
import "math"
|
|
|
|
// Here's a basic interface for geometric shapes.
|
|
type geometry interface {
|
|
area() float64
|
|
perim() float64
|
|
}
|
|
|
|
// For our example we'll implement this interface on
|
|
// `square` and `circle` types.
|
|
type square struct {
|
|
width, height float64
|
|
}
|
|
type circle struct {
|
|
radius float64
|
|
}
|
|
|
|
// To implement an interface in Go, we just need to
|
|
// implement all the methods in the interface. Here we
|
|
// implement `geometry` on `square`s.
|
|
func (s square) area() float64 {
|
|
return s.width * s.height
|
|
}
|
|
func (s square) perim() float64 {
|
|
return 2*s.width + 2*s.height
|
|
}
|
|
|
|
// The implementation for `circle`s.
|
|
func (c circle) area() float64 {
|
|
return math.Pi * c.radius * c.radius
|
|
}
|
|
func (c circle) perim() float64 {
|
|
return 2 * math.Pi * c.radius
|
|
}
|
|
|
|
// If a variable has an interface type, then we can call
|
|
// methods that are in the named interface. Here's a
|
|
// generic `measure` function taking advantage of this
|
|
// to work on any `geometry`.
|
|
func measure(g geometry) {
|
|
fmt.Println(g)
|
|
fmt.Println(g.area())
|
|
fmt.Println(g.perim())
|
|
}
|
|
|
|
func main() {
|
|
s := square{width: 3, height: 4}
|
|
c := circle{radius: 5}
|
|
|
|
// The `circle` and `square` struct types both satisfy
|
|
// the `geometry` interface so we can use instances of
|
|
// these structs as arguments to `measure.
|
|
measure(s)
|
|
measure(c)
|
|
}
|