promises

# Node.js

function asyncMethod(value) {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve("resolved: " + value);
    }, 1e3);
  });
}

function main() {
  asyncMethod("foo")
    .then((result) => console.log(result))
    .catch((err) => console.error(err));

  Promise.all([asyncMethod("A"), asyncMethod("B"), asyncMethod("C")])
    .then((result) => console.log(result))
    .catch((err) => console.error(err));
}

main();

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Output

resolved: foo
[ 'resolved: A', 'resolved: B', 'resolved: C' ]

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# Go

(closest thing is to use channels)

package main

import (
	"fmt"
	"sync"
	"time"

	"github.com/prometheus/common/log"
)

func asyncMethod(value string) chan interface{} {
	ch := make(chan interface{}, 1)
	go func() {
		time.Sleep(1 * time.Second)
		ch <- "resolved: " + value
		close(ch)
	}()

	return ch
}

func resolveAll(ch ...chan interface{}) chan interface{} {
	var wg sync.WaitGroup
	res := make([]string, len(ch))
	resCh := make(chan interface{}, 1)

	go func() {
		for i, c := range ch {
			wg.Add(1)
			go func(j int, ifcCh chan interface{}) {
				ifc := <-ifcCh
				switch v := ifc.(type) {
				case error:
					resCh <- v
				case string:
					res[j] = v
				}
				wg.Done()
			}(i, c)
		}

		wg.Wait()
		resCh <- res
		close(resCh)
	}()

	return resCh
}

func main() {
	var wg sync.WaitGroup
	wg.Add(2)

	go func() {
		result := <-asyncMethod("foo")
		switch v := result.(type) {
		case string:
			fmt.Println(v)
		case error:
			log.Errorln(v)
		}

		wg.Done()
	}()

	go func() {
		result := <-resolveAll(
			asyncMethod("A"),
			asyncMethod("B"),
			asyncMethod("C"),
		)

		switch v := result.(type) {
		case []string:
			fmt.Println(v)
		case error:
			log.Errorln(v)
		}

		wg.Done()
	}()

	wg.Wait()
}

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Output

resolved: foo
[resolved: A resolved: B resolved: C]

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编辑

#Go #Node.js

上次更新: 2022/09/30, 11:34:22

← big numbers async await→