Go学习:接口的定义和实现

与传统的面向对象不同的是,go语言的接口是由使用者定义的

package main

import "fmt"

type Retriever interface {
	Get(url string)string
}

func download(r Retriever)string{
	return r.Get("https://blog.csdn.net/qq_43135259/article/details/123293118?spm=1001.2014.3001.5502")
}

func main() {
	var r Retriever
	// runtime error: invalid memory address or nil pointer dereference
	fmt.Println(download(r))
}

只有接口没有实现,去运行是会runtime error 实现 mockretriever

package mock

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

package real

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

type Retriever struct {
	UserAgent string
	TimeOut   time.Duration
}

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)
}

package main

import (
	"fmt"
	"learngo/retriever/mock"
	real2 "learngo/retriever/real"
)

type Retriever interface {
	Get(url string) string
}

func download(r Retriever) string {
	return r.Get("https://blog.csdn.net/qq_43135259/article/details/123293118?spm=1001.2014.3001.5502")
}

func main() {
	var r Retriever = mock.Retriever{"this is fake contents"}
	// this is fake contents
	fmt.Println(download(r))
	r = real2.Retriever{}
	// HTTP/2.0 200 OK ... 
	fmt.Println(download(r))

}

go语言的实现都是隐式的,不像java一样需要implements只要实现接口里的方法就可以了