main.go：（使用者）

    1. package main
    3. import "fmt"
    5. type Retriever interface {
    6.     Get(url string) string
    7. }
    9. type Poster interface {
    10.     Post(url string, form map[string]string) string
    11. }
    13. const url = "http://www.imooc.com"
    15. func download(r Retriever) string {
    16.     return r.Get(url)
    17. }
    19. func post(poster Poster) {
    20.     poster.Post(url,
    21.                 map[string]string {
    22.                     "name": "ccmouse",
    23.                     "course": "golang",
    24.                 })
    25. }
    27. // 接口的组合：组合Retriever接口和Poster接口
    28. type RetrieverPoster interface {
    29.     Retriever
    30.     Poster
    31. }
    33. func session(s RetrieverPoster) string {
    34.     s.Post(url, map[string]string {
    35.         "contents": "another faked imooc.com",
    36.     })
    37.     return s.Get(url)
    38. }
    40. func main() {
    41.     var r Retriever
    43.     retriever := mock.Retriever{"this is a fake imooc.com"} 
    44.     r = &retriever
    45.     inspect(r) 
    47.     r = &real.Retriever{
    48.         UserAgent: "Mozilla/5.0",
    49.         TimeOut: time.Minute,
    50.     }
    51.     inspect(r)
    53.     // Type assertion
    54.     if mockRetriever, ok := r.(*mock.Retrivever); ok {
    55.         fmt.Println(mockRetriever.Contents)
    56.     } else {
    57.         fmt.Println("not a mock retriever")
    58.     }
    60.     fmt.Println("Try a session")
    61.     fmt.Println(session(&retriever)) // another faked imooc.com
    62. }
    64. func inspect(r Retriever) {
    65.     switch v := r.(type) {
    66.         case *mock.Retriever:
    67.         fmt.Println("Contents:", v.Contents)
    68.         case *real.Retriever:
    69.         fmt.Println("UserAgent:", v.UserAgent)
    70.     }
    71. }

    mockretriever.go：（实现者）

    package mock

type Retriever struct {
    Contents string
}

// 只要实现了Post方法和Get方法，就实现了RetrieverPoster接口
func (r *Retriever) Post(url string, form map[string]string) string {
    r.Contents = form["contents"]
    return "ok"
}

func (r *Retriever) Get(url string) string {
    return r.Contents
}

    retriever.go：（实现者）

    package real

import (
    "net/http"
    "net/http/httputil"
    "time"
)

type Retriever struct {
    UserAgent string
    TimeOut time.Duration
}

// 指针接收者
func (r *Retriever) Get(url string) string {
    resp, err := http.Get(url)
    if err != nil {
        panic(err)
    }

    result, err := httputil.DumpResponse(
        resp, true)

    resp.Body.Close()

    if err != nil {
        panic(err)
    }

    return string(result)
}