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()
Output
resolved: foo
[ 'resolved: A', 'resolved: B', 'resolved: C' ]
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()
}
Output
resolved: foo
[resolved: A resolved: B resolved: C]
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