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The Observer pattern involves a Publisher object notifying its subscribed Observers upon the occurrence of a specific event. The Go language offers a simple way to implement this pattern using channels.
To understand how this works, let's consider a scenario where multiple objects subscribe to a Publisher. The Publisher can then broadcast notifications to all subscribers through channels.
Here's a sample Go code that demonstrates the Observer pattern:
package main import "fmt" // Publisher is an object that can notify subscribers of an event. type Publisher struct { listeners []chan string } // Subscriber represents an object that can receive notifications from a Publisher. type Subscriber struct { ID int Channel chan string } // Sub adds a Subscriber to the Publisher's list of listeners. func (p *Publisher) Sub(sub *Subscriber) { p.listeners = append(p.listeners, sub.Channel) } // Pub sends a notification to the Publisher's subscribers. func (p *Publisher) Pub(msg string) { for _, c := range p.listeners { c <- msg } } // Run starts a Subscriber listening for notifications from the Publisher. func (s *Subscriber) Run() { for { msg := <-s.Channel fmt.Printf("Subscriber %d received: %s\n", s.ID, msg) } } func main() { // Initialize Publisher publisher := &Publisher{} // Create and add Subscribers for i := 0; i < 3; i++ { subscriber := &Subscriber{ID: i, Channel: make(chan string)} publisher.Sub(subscriber) go subscriber.Run() } // Send notifications publisher.Pub("Hello 1") publisher.Pub("Hello 2") publisher.Pub("Hello 3") }
In this example, the Publisher (Publisher) has a list of channels (listeners) where it broadcasts notifications. Subscribers (Subscriber) have their own channels (Channel) to receive notifications. When the Publisher sends a notification (Pub), it sends it to all subscribers through their channels. Each subscriber then prints the received notification. This demonstrates how the Publisher can broadcast updates to its observers.
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