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// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package event_test
import (
"fmt"
"github.com/ethereum/go-ethereum/event"
)
func ExampleFeed_acknowledgedEvents() {
// This example shows how the return value of Send can be used for request/reply
// interaction between event consumers and producers.
var feed event.Feed
type ackedEvent struct {
i int
ack chan<- struct{}
}
// Consumers wait for events on the feed and acknowledge processing.
done := make(chan struct{})
defer close(done)
for i := 0; i < 3; i++ {
ch := make(chan ackedEvent, 100)
sub := feed.Subscribe(ch)
go func() {
defer sub.Unsubscribe()
for {
select {
case ev := <-ch:
fmt.Println(ev.i) // "process" the event
ev.ack <- struct{}{}
case <-done:
return
}
}
}()
}
// The producer sends values of type ackedEvent with increasing values of i.
// It waits for all consumers to acknowledge before sending the next event.
for i := 0; i < 3; i++ {
acksignal := make(chan struct{})
n := feed.Send(ackedEvent{i, acksignal})
for ack := 0; ack < n; ack++ {
<-acksignal
}
}
// Output:
// 0
// 0
// 0
// 1
// 1
// 1
// 2
// 2
// 2
}
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