golang 接口

一、目錄結構

mock

    ---mockretriever.go

real

    ---retriever.go

main.go

mockretriever.go

package mock

import "fmt"

type Retriever struct {
	Contents string
}

func (r *Retriever) String() string {//實現了String
	return fmt.Sprintf(
		"Retriever: {Contents=%s}", r.Contents)
}

func (r *Retriever) Post(url string, //實現了Poster，如果是指針傳遞則可以改變對象屬性值
	form map[string]string) string {
	r.Contents = form["contents"]
	return "ok"
}

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

retriever.go

package real

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

type Retriever struct {
	UserAgent string
	TimeOut   time.Duration
}

func (r *Retriever) Get(url string) string {//實現了Retriever
	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)
}

main.go

package main

import (
	"fmt"
	"learn/retriever/mock"
	"learn/retriever/real"
	"time"


)

type Retriever interface {//接口定義
	Get(url string) string
}

type Poster interface {//接口定義
	Post(url string,
		form map[string]string) string
}

const url = "http://www.baidu.com"

func download(r Retriever) string {//接口使用
	return r.Get(url)
}

func post(poster Poster) {//接口使用
	poster.Post(url,
		map[string]string{
			"name":   "ccmouse",
			"course": "golang",
		})
}

type RetrieverPoster interface {//接口定義，裏面有兩個方法Get和Post
	Retriever
	Poster
}

func session(s RetrieverPoster) string {
	s.Post(url, map[string]string{ //再調用Get和Post會向下轉爲mock.Retriever的指針，可以改變對象屬性值
		"contents": "another faked baidu.com",
	})
	return s.Get(url)
}

func main() {
	var r Retriever//不用寫成指針，接口沒有指針的概念

	mockRetriever := mock.Retriever{
		Contents: "this is a fake baidu.com"}//向上轉型爲RetrieverPoster
	r = &mockRetriever//向上轉型Retriever
	inspect(r)

	r = &real.Retriever{
		UserAgent: "Mozilla/5.0",
		TimeOut:   time.Minute,
	}
	inspect(r)

	// Type assertion
	if mockRetriever, ok := r.(*mock.Retriever); ok {//判斷是哪個類實現的
		fmt.Println(mockRetriever.Contents)
	} else {
		fmt.Println("r is not a mock retriever")
	}

	fmt.Println(
		"Try a session with mockRetriever")
	fmt.Println(session(&mockRetriever))//指針傳遞，因爲mock.Retriever類定義爲指針傳遞，func (r *Retriever) String() string {}
}

func inspect(r Retriever) {
	fmt.Println("Inspecting", r)
	fmt.Printf(" > Type:%T Value:%v\n", r, r)//實現String接口，則調用實現的方法打印String
	fmt.Print(" > Type switch: ")
	switch v := r.(type) {
	case *mock.Retriever:
		fmt.Println("Contents:", v.Contents)
	case *real.Retriever:
		fmt.Println("UserAgent:", v.UserAgent)
	}
	fmt.Println()
}

輸出結果：

Inspecting Retriever: {Contents=this is a fake baidu.com}
 > Type:*mock.Retriever Value:Retriever: {Contents=this is a fake baidu.com}//實現了String接口，所以打印了我們自定義的
 > Type switch: Contents: this is a fake baidu.com

Inspecting &{Mozilla/5.0 1m0s}
 > Type:*real.Retriever Value:&{Mozilla/5.0 1m0s}
 > Type switch: UserAgent: Mozilla/5.0

r is not a mock retriever
Try a session with mockRetriever
another faked baidu.com
 

go語言中實現接口，不要指定接口名，直接實現函數就好。如果想要對象屬性，實現接口時，需要用指針傳遞。

接口本身沒有指針的說法。