共计 2403 个字符，预计需要花费 7 分钟才能阅读完成。
download: 图灵学院 JAVA 高级架构师【第四期】最新完结无密
package main
import (
"fmt"
"math/rand"
"time")
var (
Web = fakeSearch("web")
Image = fakeSearch("image")
Video = fakeSearch("video"))
type Result string
type Search func(query string) Result
func fakeSearch(kind string) Search {
return func(query string) Result {time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
return Result(fmt.Sprintf("%s result for %q\n", kind, query))
}}
func Google(query string) (results []Result) {
results = append(results, Web(query))
results = append(results, Image(query))
results = append(results, Video(query))
return}
func main() {
rand.Seed(time.Now().UnixNano())
start := time.Now()
results := Google("golang")
elapsed := time.Since(start)
fmt.Println(results)
fmt.Println(elapsed)}
运行后果如下:
[web result for “golang”
image result for “golang”
video result for “golang”
]
153.365484ms
谷歌搜寻 2.0
同时运行网页、图像和视频搜寻，并等待所有后果。没有锁，没有条件变量，没有回调。
代码如下，关注 Google 函数。
package main
import (
"fmt"
"math/rand"
"time")
var (
Web = fakeSearch("web")
Image = fakeSearch("image")
Video = fakeSearch("video"))
type Result string
type Search func(query string) Result
func fakeSearch(kind string) Search {
return func(query string) Result {time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
return Result(fmt.Sprintf("%s result for %q\n", kind, query))
}}
func Google(query string) (results []Result) {
c := make(chan Result)
go func() { c <- Web(query) } ()
go func() { c <- Image(query) } ()
go func() { c <- Video(query) } ()
for i := 0; i < 3; i++ {
result := <-c
results = append(results, result)
}
return}
func main() {
rand.Seed(time.Now().UnixNano())
start := time.Now()
results := Google("golang")
elapsed := time.Since(start)
fmt.Println(results)
fmt.Println(elapsed)}
谷歌搜寻 2.1 不要等待缓慢的服务器。没有锁，无条件变量，没有回调。通过 select 的超时实现，需要把 time.After 定义的超时通道放在 for 循环外层。
package main
import (
"fmt"
"math/rand"
"time")
var (
Web = fakeSearch("web")
Image = fakeSearch("image")
Video = fakeSearch("video"))
type Result string
type Search func(query string) Result
func fakeSearch(kind string) Search {
return func(query string) Result {time.Sleep(time.Duration(rand.Intn(100)) * time.Millisecond)
return Result(fmt.Sprintf("%s result for %q\n", kind, query))
}}
func Google(query string) (results []Result) {
c := make(chan Result)
go func() { c <- Web(query) } ()
go func() { c <- Image(query) } ()
go func() { c <- Video(query) } ()
timeout := time.After(80 * time.Millisecond)
for i := 0; i < 3; i++ {
select {
case result := <-c:
results = append(results, result)
case <-timeout:
fmt.Println("timed out")
return
}
}
return}
func main() {
rand.Seed(time.Now().UnixNano())
start := time.Now()
results := Google("golang")
elapsed := time.Since(start)
fmt.Println(results)
fmt.Println(elapsed)}