# Go接口實例

Go支持在struct類型上定義的方法。area 方法有一個 * rect類型的接收器。可以爲指針或值接收器類型定義方法。這裏是一個值接收器的例子。

circlerect結構類型都實現了幾何(geometry)接口，因此可以使用這些結構體的實例上調用measure()函數。

structs.go的完整代碼如下所示 -

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
// rect and circle types.
type rect struct {
width, height float64
}
type circle struct {
}

// To implement an interface in Go, we just need to
// implement all the methods in the interface. Here we
// implement geometry on rects.
func (r rect) area() float64 {
return r.width * r.height
}
func (r rect) perim() float64 {
return 2*r.width + 2*r.height
}

// The implementation for circles.
func (c circle) area() float64 {
}
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() {
r := rect{width: 3, height: 4}

// The circle and rect struct types both
// implement the geometry interface so we can use
// instances of
// these structs as arguments to measure.
measure(r)
measure(c)
}

F:\worksp\golang>go run interfaces.go
{3 4}
12
14
{5}
78.53981633974483
31.41592653589793