Interfaces {.en}

接口 {.zh}

::: {.en} Interfaces are named collections of method signatures. :::

::: {.zh}

接口（Interfaces）是命名了的方法签名（signatures）的集合。

:::

package main
import "fmt"
import "math"

::: {.en} Here’s a basic interface for geometric shapes. :::

::: {.zh}

这是一个几何形状的基本接口。

:::

type geometry interface {
    area() float64
    perim() float64
}

::: {.en} For our example we’ll implement this interface on rect and circle types. :::

::: {.zh}

对于我们的示例，我们将在类型 rect 和 circle 上实现此接口。

:::

type rect struct {
    width, height float64
}
type circle struct {
    radius float64
}

::: {.en} To implement an interface in Go, we just need to implement all the methods in the interface. Here we implement geometry on rects. :::

::: {.zh}

要在 Go 中实现接口，我们只需要实现接口中的所有方法。这里我们在 rect 上实现 geometry 接口。

:::

func (r rect) area() float64 {
    return r.width * r.height
}
func (r rect) perim() float64 {
    return 2*r.width + 2*r.height
}

::: {.en} The implementation for circles. :::

::: {.zh}

circle 的实现。

:::

func (c circle) area() float64 {
    return math.Pi * c.radius * c.radius
}
func (c circle) perim() float64 {
    return 2 * math.Pi * c.radius
}

::: {.en} 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. :::

::: {.zh}

如果变量具有接口类型，那么我们可以调用指定接口中的方法。这里有一个通用 measure 函数，利用它来在任何 geometry 上工作。

:::

func measure(g geometry) {
    fmt.Println(g)
    fmt.Println(g.area())
    fmt.Println(g.perim())
}
func main() {
    r := rect{width: 3, height: 4}
    c := circle{radius: 5}

::: {.en} The circle and rect struct types both implement the geometry interface so we can use instances of these structs as arguments to measure. :::

::: {.zh}

结构体类型 circle 和 rect 都实现了 geometry 接口，所以我们可以使用这些结构体的实例作为 measure 的参数。

:::

    measure(r)
    measure(c)
}

$ go run interfaces.go
{3 4}
12
14
{5}
78.53981633974483
31.41592653589793

::: {.en} To learn more about Go’s interfaces, check out this great blog post. :::

::: {.zh}

要了解有关 Go 的接口的更多信息，请查看很棒的博客文章。

:::